Package 'tf'

Convert functional data back to tabular data formats

Description

Various converters to turn tfb- or tfd-vectors into data.frames or matrices, or even an actual R function.

Usage

## S3 method for class 'tf'
as.data.frame(x, row.names = NULL, optional = FALSE, unnest = FALSE, ...)

## S3 method for class 'tf'
as.matrix(x, arg, interpolate = FALSE, ...)

## S3 method for class 'tf'
as.function(x, ...)

Arguments

x	a tf object
row.names	NULL or a character vector giving the row names for the data frame. Missing values are not allowed.
optional	not used
unnest	if TRUE, the function will return a data.frame with the evaluated functions.
...	additional arguments to be passed to or from methods.
arg	a vector of argument values / evaluation points for x. Defaults to tf_arg(x).
interpolate	should functions be evaluated (i.e., inter-/extrapolated) for values in arg for which no original data is available? Only relevant for the raw data class tfd, for which it defaults to FALSE. Basis-represented functional data tfb are always "interpolated".

Value

for as.data.frame.tf: if unnest is FALSE (default), a one-column data.frame with a tf-column containing x. if unnest is TRUE, a 3-column data frame with columns id for the (unique) names of x or a numeric identifier, arg and value, with each row containing one function evaluation at the original arg-values.

for as.matrix.tf: a matrix with one row per function and one column per arg.

for as.function.tf: an R function with argument arg that evaluates x on arg and returns the list of function values

---

Turns any object into a list

Description

See above.

Usage

ensure_list(x)

Arguments

x

any input

Value

x turned into a list.

See Also

Other tidyfun developer tools: prep_plotting_arg(), unique_id()

---

Eigenfunctions via weighted, regularized SVD

Description

Compute (truncated) orthonormal eigenfunctions and scores for (partially missing) data on a common (potentially non-equidistant) grid.

Usage

fpc_wsvd(data, arg, pve = 0.995)

## S3 method for class 'matrix'
fpc_wsvd(data, arg, pve = 0.995)

## S3 method for class 'data.frame'
fpc_wsvd(data, arg, pve = 0.995)

Arguments

data	numeric matrix of function evaluations (each row is one curve, no NAs)
arg	numeric vector of argument values
pve	percentage of variance explained

Details

Performs a weighted SVD with trapezoidal quadrature weights s.t. returned vectors represent (evaluations of) orthonormal eigenfunctions $\phi_j(t)$, not eigenvectors $\phi_j = (\phi_j(t_1), \dots, \phi_j(t_n))$, specifically:
$\int_T \phi_j(t)^2 dt \approx \sum_i \Delta_i \phi_j(t_i)^2 = 1$ given quadrature weights $\Delta_i$, not $\phi_j'\phi_j = \sum_i \phi_j(t_i)^2 = 1$;
$\int_T \phi_j(t) \phi_k(t) dt = 0$ not $\phi_j'\phi_k = \sum_i \phi_j(t_i)\phi_k(t_i) = 0$, c.f. mogsa::wsvd().
For incomplete data, this uses an adaptation of softImpute::softImpute(), see references. Note that will not work well for data on a common grid if more than a few percent of data points are missing, and it breaks down completely for truly irregular data with no/few common timepoints, even if observed very densely. For such data, either re-evaluate on a common grid first or use more advanced FPCA approaches like refund::fpca_sc(), see last example for tfb_fpc()

Value

a list with entries

• mu estimated mean function (numeric vector)

• efunctions estimated FPCs (numeric matrix, columns represent FPCs)

• scores estimated FPC scores (one row per observed curve)

• npc how many FPCs were returned for the given pve (integer)

• scoring_function a function that returns FPC scores for new data and given eigenfunctions, see tf:::.fpc_wsvd_scores for an example.

Author(s)

Trevor Hastie, Rahul Mazumder, Cheng Meng, Fabian Scheipl

References

code adapted from / inspired by mogsa::wsvd() by Cheng Meng and softImpute::softImpute() by Trevor Hastie and Rahul Mazumder.
Meng C (2023). mogsa: Multiple omics data integrative clustering and gene set analysis. https://bioconductor.org/packages/mogsa.

Mazumder, Rahul, Hastie, Trevor, Tibshirani, Robert (2010). “Spectral regularization algorithms for learning large incomplete matrices.” The Journal of Machine Learning Research, 11, 2287-2322.

Hastie T, Mazumder R (2021). softImpute: Matrix Completion via Iterative Soft-Thresholded SVD. R package version 1.4-1, https://CRAN.R-project.org/package=softImpute.

See Also

Other tfb-class: tfb, tfb_fpc(), tfb_spline()

Other tfb_fpc-class: tfb_fpc()

---

Summarize each tf in a vector

Description

These functions extract (user-specified) function-wise summary statistics from each entry in a tf-vector. To summarize a vector of functions at each argument value, see ?tfsummaries. Note that these will tend to yield lots of NAs for irregular tfd unless you set a tf_evaluator()-function that does inter- and extrapolation for them beforehand.

Usage

tf_fwise(x, .f, arg = tf_arg(x), ...)

tf_fmax(x, arg = tf_arg(x), na.rm = FALSE)

tf_fmin(x, arg = tf_arg(x), na.rm = FALSE)

tf_fmedian(x, arg = tf_arg(x), na.rm = FALSE)

tf_frange(x, arg = tf_arg(x), na.rm = FALSE, finite = FALSE)

tf_fmean(x, arg = tf_arg(x))

tf_fvar(x, arg = tf_arg(x))

tf_fsd(x, arg = tf_arg(x))

tf_crosscov(x, y, arg = tf_arg(x))

tf_crosscor(x, y, arg = tf_arg(x))

Arguments

x	a tf object
.f	a function or formula that is applied to each entry of x, see purrr::as_mapper() and Details.
arg	defaults to standard argument values of x
...	additional arguments for purrr::as_mapper()
na.rm	a logical indicating whether missing values should be removed.
finite	logical, indicating if all non-finite elements should be omitted.
y	a tf object

Details

tf_fwise turns x into a list of data.frames with columns arg and values internally, so the function/formula in .f gets a data.frame .x with these columns, see examples below or source code for tf_fmin(), tf_fmax(), etc

Value

a list (or vector) of the same length as x with the respective summaries

Functions

• tf_fwise(): User-specified function-wise summary statistics

• tf_fmax(): maximal value of each function

• tf_fmin(): minimal value of each function

• tf_fmedian(): median value of each function

• tf_frange(): range of values of each function

• tf_fmean(): mean of each function: $\tfrac{1}{|T|}\int_T x_i(t) dt$

• tf_fvar(): variance of each function: $\tfrac{1}{|T|}\int_T (x_i(t) - \bar x(t))^2 dt$

• tf_fsd(): standard deviation of each function: $\sqrt{\tfrac{1}{|T|}\int_T (x_i(t) - \bar x(t))^2 dt}$

• tf_crosscov(): cross-covariances between two functional vectors: $\tfrac{1}{|T|}\int_T (x_i(t) - \bar x(t)) (y_i(t)-\bar y(t)) dt$

• tf_crosscor(): cross-correlation between two functional vectors: tf_crosscov(x, y) / (tf_fsd(x) * tf_fsd(y))

See Also

Other tidyfun summary functions: tfsummaries

Examples

x <- tf_rgp(3)
layout(t(1:3))
plot(x, col = 1:3)
#  each function's values to [0,1]:
x_clamp <- (x - tf_fmin(x)) / (tf_fmax(x) - tf_fmin(x))
plot(x_clamp, col = 1:3)
# standardize each function to have mean / integral 0 and sd 1:
x_std <- (x - tf_fmean(x)) / tf_fsd(x)
tf_fvar(x_std) == c(1, 1, 1)
plot(x_std, col = 1:3)
# Custom functions:
# 80%tiles of each function's values:
tf_fwise(x, ~ quantile(.x$value, 0.8)) |> unlist()
# minimal value of each function for t > 0.5
tf_fwise(x, ~ min(.x$value[.x$arg > 0.5])) |> unlist()

tf_crosscor(x, -x)
tf_crosscov(x, x) == tf_fvar(x)

---

Find out if values are inside given bounds

Description

in_range and its infix-equivalent ⁠%inr%⁠ return TRUE for all values in the numeric vector f that are within the range of values in r.

Usage

in_range(f, r)

f %inr% r

Arguments

f	a numeric vector
r	numeric vector used to specify a range, only the minimum and maximum of r are used.

Value

a logical vector of the same length as f

See Also

Other tidyfun utility functions: tf_arg(), tf_zoom()

---

Math, Summary and Ops Methods for tf

Description

These methods and operators mostly work arg-value-wise on tf objects, see ?groupGeneric for implementation details.

Usage

## S3 method for class 'tf'
Ops(e1, e2)

## S3 method for class 'tfd'
e1 == e2

## S3 method for class 'tfd'
e1 != e2

## S3 method for class 'tfb'
e1 == e2

## S3 method for class 'tfb'
e1 != e2

## S3 method for class 'tfd'
Ops(e1, e2)

## S3 method for class 'tfb'
Ops(e1, e2)

## S3 method for class 'tfd'
Math(x, ...)

## S3 method for class 'tfb'
Math(x, ...)

## S3 method for class 'tf'
Summary(...)

## S3 method for class 'tfd'
cummax(...)

## S3 method for class 'tfd'
cummin(...)

## S3 method for class 'tfd'
cumsum(...)

## S3 method for class 'tfd'
cumprod(...)

## S3 method for class 'tfb'
cummax(...)

## S3 method for class 'tfb'
cummin(...)

## S3 method for class 'tfb'
cumsum(...)

## S3 method for class 'tfb'
cumprod(...)

Arguments

e1	an tf or a numeric vector
e2	an tf or a numeric vector
x	an tf
...	tf-objects (not used for Math group generic)

Details

See examples below. Equality checks of functional objects are even more iffy than usual for computer math and not very reliable. Note that max and min are not guaranteed to be maximal/minimal over the entire domain, only on the evaluation grid used for computation. With the exception of addition and multiplication, operations on tfb-objects first evaluate the data on their arg, perform computations on these evaluations and then convert back to an tfb- object, so a loss of precision should be expected – especially so for small spline bases and/or very wiggly data.

Value

a tf- or logical vector with the computed result

See Also

tf_fwise() for scalar summaries of each function in a tf-vector

Examples

set.seed(1859)
f <- tf_rgp(4)
2 * f == f + f
sum(f) == f[1] + f[2] + f[3] + f[4]
log(exp(f)) == f
plot(f, points = FALSE)
lines(range(f), col = 2, lty = 2)

f2 <- tf_rgp(5) |> exp() |> tfb(k = 25)
layout(t(1:3))
plot(f2, col = gray.colors(5))
plot(cummin(f2), col = gray.colors(5))
plot(cumsum(f2), col = gray.colors(5))

# ?tf_integrate for integrals, ?tf_fwise for scalar summaries of each function

---

base plots for tfs

Description

Some base functions for displaying functional data in spaghetti- (i.e., line plots) and lasagna- (i.e., heat map) flavors.

Usage

## S3 method for class 'tf'
plot(
  x,
  y,
  n_grid = 50,
  points = is_irreg(x),
  type = c("spaghetti", "lasagna"),
  alpha = min(1, max(0.05, 2/length(x))),
  ...
)

## S3 method for class 'tf'
lines(x, arg, n_grid = 50, alpha = min(1, max(0.05, 2/length(x))), ...)

## S3 method for class 'tf'
points(
  x,
  arg,
  n_grid = NA,
  alpha = min(1, max(0.05, 2/length(x))),
  interpolate = FALSE,
  ...
)

Arguments

x	an tf object
y	(optional) numeric vector to be used as arg (i.e., for the x-axis...!)
n_grid	minimal size of equidistant grid used for plotting, defaults to 50. See details.
points	should the original evaluation points be marked by points? Defaults to TRUE for irregular tfd and FALSE for all others
type	"spaghetti": line plots, "lasagna": heat maps.
alpha	alpha-value (seegrDevices::rgb()) for noodle transparency. Defaults to 2/(no. of observations). Lower is more transparent.
...	additional arguments for matplot() ("spaghetti") or image() ("lasagna")
arg	evaluation grid (vector)
interpolate	should functions be evaluated (i.e., inter-/extrapolated) for arg for which no original data is available? Only relevant for tfd, defaults to FALSE

Details

If no second argument y is given, evaluation points (arg) for the functions are given by the union of the tf's arg and an equidistant grid over its domain with n_grid points. If you want to only see the original data for tfd-objects without inter-/extrapolation, use n_grid < 1 or n_grid = NA.

Value

the plotted tf-object, invisibly.

References

Swihart, J B, Caffo, Brian, James, D B, Strand, Matthew, Schwartz, S B, Punjabi, M N (2010). “Lasagna plots: a saucy alternative to spaghetti plots.” Epidemiology (Cambridge, Mass.), 21(5), 621–625.

---

Preprocess evaluation grid for plotting

Description

(internal function exported for re-use in upstream packages)

Usage

prep_plotting_arg(f, n_grid)

Arguments

f	a tf-object
n_grid	length of evaluation grid

Value

a semi-regular grid rounded down to appropriate resolution

See Also

Other tidyfun developer tools: ensure_list(), unique_id()

---

Pretty printing and formatting for functional data

Description

Print/format tf-objects.

Usage

## S3 method for class 'tf'
print(x, n = 5, ...)

## S3 method for class 'tfd_reg'
print(x, n = 5, ...)

## S3 method for class 'tfd_irreg'
print(x, n = 5, ...)

## S3 method for class 'tfb'
print(x, n = 5, ...)

## S3 method for class 'tf'
format(
  x,
  digits = 2,
  nsmall = 0,
  width = options()$width,
  n = 5,
  prefix = TRUE,
  ...
)

Arguments

x	any R object (conceptually); typically numeric.
n	how many elements of x to print out
...	further arguments passed to or from other methods.
digits	a positive integer indicating how many significant digits are to be used for numeric and complex x. The default, NULL, uses getOption("digits"). This is a suggestion: enough decimal places will be used so that the smallest (in magnitude) number has this many significant digits, and also to satisfy nsmall. (For more, notably the interpretation for complex numbers see signif.)
nsmall	the minimum number of digits to the right of the decimal point in formatting real/complex numbers in non-scientific formats. Allowed values are 0 <= nsmall <= 20.
width	default method: the minimum field width or NULL or 0 for no restriction. AsIs method: the maximum field width for non-character objects. NULL corresponds to the default 12.
prefix	used internally.

Value

prints out x and returns it invisibly

---

Inter- and extrapolation functions for tfd-objects

Description

These are the currently available evaluator-functions for tfd-objects, which control how the entries are inter-/extrapolated to previously unseen arg-values. They all are merely wrappers around zoo::na.fill(), zoo::na.approx(), etc... Note that these are not meant to be called directly – they are internal functions used by tf_evaluate.tfd() to do its thing.

The list:

• tf_approx_linear for linear interpolation without extrapolation (i.e., zoo::na.approx() with na.rm = FALSE) – this is the default,

• tf_approx_spline for cubic spline interpolation, (i.e., zoo::na.spline() with na.rm = FALSE),

• tf_approx_none in order to not inter-/extrapolate ever (i.e., zoo::na.fill() with fill = NA)

• tf_approx_fill_extend for linear interpolation and constant extrapolation (i.e., zoo::na.fill() with fill = "extend")

• tf_approx_locf for "last observation carried forward" (i.e., zoo::na.locf() with na.rm = FALSE and

• tf_approx_nocb for "next observation carried backward" (i.e., zoo::na.locf() with ⁠na.rm = FALSE, fromLast = TRUE⁠).

For implementing your own, see source code of tf:::zoo_wrapper.

Usage

tf_approx_linear(x, arg, evaluations)

tf_approx_spline(x, arg, evaluations)

tf_approx_none(x, arg, evaluations)

tf_approx_fill_extend(x, arg, evaluations)

tf_approx_locf(x, arg, evaluations)

tf_approx_nocb(x, arg, evaluations)

Arguments

x	new arg values to approximate/interpolate/extrapolate the function for
arg	the arg values of the evaluations
evaluations	the function values at arg

Value

a vector of values of the function defined by the given $(x_i, f(x_i))$=⁠(arg, evaluations)⁠-tuples at new argument values x.

See Also

tfd

Other tidyfun inter/extrapolation functions: tf_evaluate(), tf_interpolate()

Other tidyfun inter/extrapolation functions: tf_evaluate(), tf_interpolate()

Other tidyfun inter/extrapolation functions: tf_evaluate(), tf_interpolate()

Other tidyfun inter/extrapolation functions: tf_evaluate(), tf_interpolate()

Other tidyfun inter/extrapolation functions: tf_evaluate(), tf_interpolate()

Other tidyfun inter/extrapolation functions: tf_evaluate(), tf_interpolate()

---

Utility functions for tf-objects

Description

A bunch of methods & utilities that do what they say: get or set the respective attributes of a tf-object.

Usage

tf_arg(f)

tf_evaluations(f)

tf_count(f)

tf_domain(f)

tf_domain(x) <- value

tf_evaluator(f)

tf_evaluator(x) <- value

tf_basis(f, as_tfd = FALSE)

tf_arg(x) <- value

## S3 replacement method for class 'tfd_irreg'
tf_arg(x) <- value

## S3 replacement method for class 'tfd_reg'
tf_arg(x) <- value

## S3 replacement method for class 'tfb'
tf_arg(x) <- value

## S3 method for class 'tfb'
coef(object, ...)

## S3 method for class 'tf'
rev(x)

## S3 method for class 'tf'
is.na(x)

## S3 method for class 'tfd_irreg'
is.na(x)

is_tf(x)

is_tfd(x)

is_reg(x)

is_tfd_reg(x)

is_irreg(x)

is_tfd_irreg(x)

is_tfb(x)

is_tfb_spline(x)

is_tfb_fpc(x)

Arguments

f	an tf object
x	an tf object
value	for ⁠tf_evaluator<-⁠: (bare or quoted) name of a function that can be used to interpolate an tfd. Needs to accept vector arguments x, arg, evaluations and return evaluations of the function defined by arg, evaluations at x. for ⁠tf_arg<-⁠: (list of) new arg-values. for ⁠tf_domain<-⁠: sorted numeric vector with the 2 new endpoints of the domain.
as_tfd	should the basis be returned as a tfd-vector evaluated on tf_arg(f)? Defaults to FALSE, which returns the matrix of basis functions (columns) evaluated on tf_arg(f) (rows).
object	as usual
...	dots

Value

either the respective attribute or, for setters (assignment functions), the input object with modified properties.

See Also

Other tidyfun utility functions: in_range(), tf_zoom()

---

Functional Data Depth

Description

Data depths for functional data. Currently implemented: Modified Band-2 Depth, see reference.

Usage

tf_depth(x, arg, depth = "MBD", na.rm = TRUE, ...)

## S3 method for class 'matrix'
tf_depth(x, arg, depth = "MBD", na.rm = TRUE, ...)

## S3 method for class 'tf'
tf_depth(x, arg, depth = "MBD", na.rm = TRUE, ...)

Arguments

x	tf (or a matrix of evaluations)
arg	grid of evaluation points
depth	currently available: "MBD", i.e. modified band depth
na.rm	TRUE remove missing observations?
...	further arguments handed to the function computing the respective tf_depth.

Value

vector of tf_depth values

References

Sun, Ying, Genton, G M, Nychka, W D (2012). “Exact fast computation of band depth for large functional datasets: How quickly can one million curves be ranked?” Stat, 1(1), 68–74.

López-Pintado, Sara, Romo, Juan (2009). “On the concept of depth for functional data.” Journal of the American statistical Association, 104(486), 718–734.

---

Differentiating functional data: approximating derivative functions

Description

Derivatives of tf-objects use finite differences of the evaluations for tfd and finite differences of the basis functions for tfb.

Usage

tf_derive(f, arg, order = 1, ...)

## S3 method for class 'matrix'
tf_derive(f, arg, order = 1, ...)

## S3 method for class 'tfd'
tf_derive(f, arg, order = 1, ...)

## S3 method for class 'tfb_spline'
tf_derive(f, arg, order = 1, ...)

## S3 method for class 'tfb_fpc'
tf_derive(f, arg, order = 1, ...)

Arguments

f	a tf-object
arg	grid to use for the finite differences. Not the arg of the returned object for tfd-inputs, see Details.
order	order of differentiation. Maximal value for tfb_spline is 2.
...	not used

Details

The derivatives of tfd objects use centered finite differences, e.g. for first derivatives $f'((t_i + t_{i+1})/2) \approx \frac{f(t_i) + f(t_{i+1})}{t_{i+1} - t_i}$, so the domains of differentiated tfd will shrink (slightly) at both ends. Unless the tfd has a rather fine and regular grid, representing the data in a suitable basis representation with tfb() and then computing the derivatives or integrals of those is usually preferable.

Note that, for some spline bases like "cr" or "tp" which always begin/end linearly, computing second derivatives will produce artefacts at the outer limits of the functions' domain due to these boundary constraints. Basis "bs" does not have this problem for sufficiently high orders, but tends to yield slightly less stable fits.

Value

a tf (with slightly different arg or basis for the derivatives, see Details)

Methods (by class)

• tf_derive(matrix): row-wise finite differences

• tf_derive(tfd): derivatives by finite differencing.

• tf_derive(tfb_spline): derivatives by finite differencing.

• tf_derive(tfb_fpc): derivatives by finite differencing.

See Also

Other tidyfun calculus functions: tf_integrate()

---

Evaluate tf-vectors for given argument values

Description

Also used internally by the [-operator for tf data (see ?tfbrackets) to evaluate object, see examples.

Usage

tf_evaluate(object, arg, ...)

## Default S3 method:
tf_evaluate(object, arg, ...)

## S3 method for class 'tfd'
tf_evaluate(object, arg, evaluator = tf_evaluator(object), ...)

## S3 method for class 'tfb'
tf_evaluate(object, arg, ...)

Arguments

object	a tf, or a data.frame-like object with tf columns.
arg	optional evaluation grid (vector or list of vectors). Defaults to tf_arg(object), implicitly.
...	not used
evaluator	optional. The function to use for inter/extrapolating the tfd. Defaults to tf_evaluator(object). See e.g. tf_approx_linear() for details.

Value

A list of numeric vectors containing the function evaluations on arg.

See Also

Other tidyfun inter/extrapolation functions: tf_approx_linear(), tf_interpolate()

Examples

f <- tf_rgp(3, arg = seq(0, 1, length.out = 11))
tf_evaluate(f) |> str()
tf_evaluate(f, arg = 0.5) |> str()
# equivalent, as matrix:
f[, 0.5]
new_grid <- seq(0, 1, length.out = 6)
tf_evaluate(f, arg = new_grid) |> str()
# equivalent, as matrix:
f[, new_grid]

---

Integrals and anti-derivatives of functional data

Description

Integrals of tf-objects are computed by simple quadrature (trapezoid rule). By default the scalar definite integral $\int^{upper}_{lower}f(s)ds$ is returned (option definite = TRUE), alternatively for definite = FALSE the anti-derivative on ⁠[lower, upper]⁠, e.g. a tfd or tfb object representing $F(t) \approx \int^{t}_{lower}f(s)ds$, for $t \in$⁠[lower, upper]⁠, is returned.

Usage

tf_integrate(f, arg, lower, upper, ...)

## Default S3 method:
tf_integrate(f, arg, lower, upper, ...)

## S3 method for class 'tfd'
tf_integrate(
  f,
  arg,
  lower = tf_domain(f)[1],
  upper = tf_domain(f)[2],
  definite = TRUE,
  ...
)

## S3 method for class 'tfb'
tf_integrate(
  f,
  arg,
  lower = tf_domain(f)[1],
  upper = tf_domain(f)[2],
  definite = TRUE,
  ...
)

Arguments

f	a tf-object
arg	(optional) grid to use for the quadrature.
lower	lower limits of the integration range. For definite=TRUE, this can be a vector of the same length as f.
upper	upper limits of the integration range (but see definite arg / Description). For definite=TRUE, this can be a vector of the same length as f.
...	not used
definite	should the definite integral be returned (default) or the antiderivative. See Description.

Value

For definite = TRUE, the definite integrals of the functions in f. For definite = FALSE and tf-inputs, a tf object containing their anti-derivatives

See Also

Other tidyfun calculus functions: tf_derive()

---

Re-evaluate tf-objects on a new grid of argument values.

Description

Change the internal representation of a tf-object so that it uses a different grid of argument values (arg). Useful for

• thinning out dense grids to make data smaller

• filling out sparse grids to make derivatives/integrals and locating extrema or zero crossings more accurate (... if the interpolation works well ...)

• making irregular functional data into (more) regular data.

For tfd-objects, this is just syntactic sugar for tfd(object, arg = arg). To inter/extrapolate more reliably and avoid NAs, call tf_interpolate with evaluator = tf_approx_fill_extend.
For tfb-objects, this re-evaluates basis functions on the new grid which can speed up subsequent computations if they all use that grid. NB: To reliably impute very irregular data on a regular, common grid, you'll be better off doing FPCA-based imputation or other model-based approaches in most cases.

Usage

tf_interpolate(object, arg, ...)

## S3 method for class 'tfb'
tf_interpolate(object, arg, ...)

## S3 method for class 'tfd'
tf_interpolate(object, arg, ...)

Arguments

object	an object inheriting from tf
arg	a vector of argument values on which to evaluate the functions in object
...	additional arguments handed over to tfd or tfb, for the construction of the returned object

Value

a tfd or tfb object on the new grid given by arg

See Also

tf_rebase(), which is more general.

Other tidyfun inter/extrapolation functions: tf_approx_linear(), tf_evaluate()

Examples

# thinning out a densely observed tfd
dense <- tf_rgp(10, arg = seq(0, 1, length.out = 1001))
less_dense <- tf_interpolate(dense, arg = seq(0, 1, length.out = 101))
dense
less_dense
# filling out sparse data (use a suitable evaluator-function!)
sparse <- tf_rgp(10, arg = seq(0, 5, length.out = 11))
plot(sparse, points = TRUE)
# change evaluator for better interpolation
tfd(sparse, evaluator = tf_approx_spline) |>
  tf_interpolate(arg = seq(0, 5, length.out = 201)) |>
  lines(col = 2, lty = 2)

set.seed(1860)
sparse_irregular <- tf_rgp(5) |>
  tf_sparsify(0.5) |>
  tf_jiggle()
tf_interpolate(sparse_irregular, arg = seq(0, 1, length.out = 51))

---

Make a tf (more) irregular

Description

Randomly create some irregular functional data from regular ones. jiggle it by randomly moving around its arg-values. Only for tfd. sparsify it by setting (100*dropout)% of its values to NA.

Usage

tf_jiggle(f, amount = 0.4, ...)

tf_sparsify(f, dropout = 0.5, ...)

Arguments

f	a tfd object
amount	how far away from original grid points can the new grid points lie, at most (relative to original distance to neighboring grid points). Defaults to at most 40% (0.4) of the original grid distances. Must be lower than 0.5
...	additional args for the returned tfd in tf_jiggle
dropout	how many values of f to drop, defaults to 50%.

Value

an (irregular) tfd object

See Also

Other tidyfun RNG functions: tf_rgp()

Other tidyfun RNG functions: tf_rgp()

---

Change (basis) representation of a tf-object

Description

Apply the representation of one tf-object to another; i.e. re-express it in the other's basis, on its grid, etc.
Useful for making different functional data objects compatible so they can be combined, compared or computed with.

Usage

tf_rebase(object, basis_from, arg = tf_arg(basis_from), ...)

## S3 method for class 'tfd'
tf_rebase(object, basis_from, arg = tf_arg(basis_from), ...)

## S3 method for class 'tfb'
tf_rebase(object, basis_from, arg = tf_arg(basis_from), ...)

Arguments

object	a tf object whose representation should be changed
basis_from	the tf object with the desired basis, arg, evaluator, etc.
arg	optional new arg values, defaults to those of basis_from
...	forwarded to the tfb or tfd constructors

Details

This uses double dispatch (S3) internally, so the methods defined below are themselves generics for methods tf_rebase.tfd.tfd, tf_rebase.tfd.tfb_spline, tf_rebase.tfd.tfb_fpc, tf_rebase.tfb.tfd, tf_rebase.tfb.tfb that dispatch on object_from.

Value

a tf-vector containing the data of object in the same representation as basis_from (potentially modified by the arguments given in ...).

Methods (by class)

• tf_rebase(tfd): re-express a tfd-vector in the same representation as some other tf-vector

• tf_rebase(tfb): re-express a tfb-vector in the same representation as some other tf-vector.

---

Gaussian Process random generator

Description

Generates n realizations of a zero-mean Gaussian process. The function also accepts user-defined covariance functions (without "nugget" effect, see cov), The implemented defaults with scale parameter $\phi$, order $o$ and nugget effect variance $\sigma^2$ are:

• squared exponential covariance $Cov(x(t), x(t')) = \exp(-(t-t')^2)/\phi) + \sigma^2 \delta_{t}(t')$.

• Wiener process covariance $Cov(x(t), x(t')) = \min(t',t)/\phi + \sigma^2 \delta_{t}(t')$,

• Matèrn process covariance $Cov(x(t), x(t')) = \tfrac{2^{1-o}}{\Gamma(o)} (\tfrac{\sqrt{2o}|t-t'|}{\phi})^o \text{Bessel}_o(\tfrac{\sqrt{2o}|t-t'|}{s}) + \sigma^2 \delta_{t}(t')$

Usage

tf_rgp(
  n,
  arg = 51L,
  cov = c("squareexp", "wiener", "matern"),
  scale = diff(range(arg))/10,
  nugget = scale/200,
  order = 1.5
)

Arguments

n	how many realizations to draw
arg	vector of evaluation points (arg of the return object). Defaults to (0, 0.02, 0.04, ..., 1). If given as a single integer (don't forget the L...), creates a regular grid of that length over (0,1).
cov	type of covariance function to use. Implemented defaults are "squareexp", "wiener", "matern", see Description. Can also be any vectorized function returning $Cov(x(t), x(t'))$ without nugget effect for pairs of inputs t and t'.
scale	scale parameter (see Description). Defaults to the width of the domain divided by 10.
nugget	nugget effect for additional white noise / unstructured variability. Defaults to scale/200 (so: very little white noise).
order	order of the Matèrn covariance (if used, must be >0), defaults to 1.5. The higher, the smoother the process. Evaluation of the covariance function becomes numerically unstable for large (>20) order, use "squareexp".

Value

an tfd-vector of length n

See Also

Other tidyfun RNG functions: tf_jiggle()

---

Simple smoothing of tf objects

Description

Apply running means or medians, lowess or Savitzky-Golay filtering to smooth functional data. This does nothing for tfb-objects, which should be smoothed by using a smaller basis / stronger penalty.

Usage

tf_smooth(x, ...)

## S3 method for class 'tfb'
tf_smooth(x, verbose = TRUE, ...)

## S3 method for class 'tfd'
tf_smooth(
  x,
  method = c("lowess", "rollmean", "rollmedian", "savgol"),
  verbose = TRUE,
  ...
)

Arguments

x	a tf object containing functional data
...	arguments for the respective method. See Details.
verbose	give lots of diagnostic messages? Defaults to TRUE
method	one of "lowess" (see stats::lowess()), "rollmean", "rollmedian" (see zoo::rollmean()) or "savgol" (see pracma::savgol())

Details

tf_smooth.tfd overrides/automatically sets some defaults of the used methods:

• lowess uses a span parameter of f = 0.15 (instead of 0.75) by default.

• rollmean/median use a window size of k = $<$number of grid points$>$/20 (i.e., the nearest odd integer to that) and sets fill= "extend" (i.e., constant extrapolation to replace missing values at the extremes of the domain) by default. Use fill= NA for zoo's default behavior of shortening the smoothed series.

• savgol uses a window size of k = $<$number of grid points$>$/10 (i.e., the nearest odd integer to that).

Value

a smoothed version of the input. For some methods/options, the smoothed functions may be shorter than the original ones (at both ends).

Examples

library(zoo)
library(pracma)
f <- tf_sparsify(tf_jiggle(tf_rgp(4, 201, nugget = 0.05)))
f_lowess <- tf_smooth(f, "lowess")
# these methods ignore the distances between arg-values:
f_mean <- tf_smooth(f, "rollmean")
f_median <- tf_smooth(f, "rollmean", k = 31)
f_sg <- tf_smooth(f, "savgol", fl = 31)
layout(t(1:4))
plot(f, points = FALSE, main = "original")
plot(f_lowess,
  points = FALSE, col = "blue", main = "lowess (default,\n span 0.9 in red)"
)
lines(tf_smooth(f, "lowess", f = 0.9), col = "red", alpha = 0.2)
plot(f_mean,
  points = FALSE, col = "blue", main = "rolling means &\n medians (red)"
)
lines(f_median, col = "red", alpha = 0.2) # note constant extrapolation at both ends!
plot(f, points = FALSE, main = "orginal and\n savgol (red)")
lines(f_sg, col = "red")

---

Find out where functional data fulfills certain conditions.

Description

tf_where allows to define a logical expression about the function values and returns the argument values for which that condition is true.
tf_anywhere is syntactic sugar for tf_where with return = "any" to get a logical flag for each function if the condition is TRUE anywhere, see below.

Usage

tf_where(f, cond, return = c("all", "first", "last", "range", "any"), arg)

tf_anywhere(f, cond, arg)

Arguments

f	a tf object
cond	a logical expression about value (and/or arg) that defines a condition about the functions, see examples and details.
return	for each entry in f, tf_where either returns all arg for which cond is true, the first, the last or their range or logical flags whether the functions fullfill the condition anywhere. For "range", note that cond may not be true for all arg values in this range, though, this is not checked.
arg	optional arg-values on which to evaluate f and check cond, defaults to tf_arg(f).

Details

Entries in f that do not fulfill cond anywhere yield numeric(0).
cond is evaluated as a base::subset()-statement on a data.frame containing a single entry in f with columns arg and value, so most of the usual dplyr tricks are available as well, see examples.
Any condition evaluates to NA on NA-entries in f.

Value

depends on return:

• return = "any", i.e, anywhere: a logical vector of the same length as f.

• return = "all": a list of vectors of the same length as f, with empty vectors for the functions that never fulfill the condition.

• return = "range": a data frame with columns "begin" and "end".

• else, a numeric vector of the same length as f with NA for entries of f that nowhere fulfill the condition.

Examples

lin <- 1:4 * tfd(seq(-1, 1, length.out = 11), seq(-1, 1, length.out = 11))
tf_where(lin, value %inr% c(-1, 0.5))
tf_where(lin, value %inr% c(-1, 0.5), "range")
a <- 1
tf_where(lin, value > a, "first")
tf_where(lin, value < a, "last")
tf_where(lin, value > 2, "any")
tf_anywhere(lin, value > 2)

set.seed(4353)
f <- tf_rgp(5, 11)
plot(f, pch = as.character(1:5), points = TRUE)
tf_where(f, value == max(value))
# where is the function increasing/decreasing?
tf_where(f, value > dplyr::lag(value, 1, value[1]))
tf_where(f, value < dplyr::lead(value, 1, tail(value, 1)))
# where are the (interior) extreme points (sign changes of `diff(value)`)?
tf_where(
  f,
  sign(c(diff(value)[1], diff(value))) !=
    sign(c(diff(value), tail(diff(value), 1)))
)
# where in its second half is the function positive?
tf_where(f, arg > 0.5 & value > 0)
# does the function ever exceed?
tf_anywhere(f, value > 1)

---

Functions to zoom in/out on functions

Description

These are used to redefine or restrict the domain of tf objects.

Usage

tf_zoom(f, begin, end, ...)

## S3 method for class 'tfd'
tf_zoom(f, begin = tf_domain(f)[1], end = tf_domain(f)[2], ...)

## S3 method for class 'tfb'
tf_zoom(f, begin = tf_domain(f)[1], end = tf_domain(f)[2], ...)

## S3 method for class 'tfb_fpc'
tf_zoom(f, begin = tf_domain(f)[1], end = tf_domain(f)[2], ...)

Arguments

f	a tf-object
begin	numeric vector of length 1 or length(f). Defaults to the lower limit of the domain of f.
end	numeric vector of length 1 or length(f). Defaults to the upper limit of the domain of f.
...	not used

Value

an object like f on a new domain (potentially). Note that regular functional data and functions in basis representation will be turned into irregular tfd-objects iff begin or end are not scalar.

See Also

Other tidyfun utility functions: in_range(), tf_arg()

Examples

x <- tf_rgp(10)
plot(x)
tf_zoom(x, 0.5, 0.9)
tf_zoom(x, 0.5, 0.9) |> lines(col = "red")
tf_zoom(x, seq(0, 0.5, length.out = 10), seq(0.5, 1, length.out = 10)) |>
  lines(col = "blue", lty = 3)

---

Constructors for functional data in basis representation

Description

Various constructors for tfb-vectors from different kinds of inputs.

Usage

tfb(
  data = data_frame(.name_repair = "minimal"),
  basis = c("spline", "fpc", "wavelet"),
  ...
)

tfb_wavelet(data, ...)

as.tfb(data, basis = c("spline", "fpc"), ...)

Arguments

data	a matrix, data.frame or list of suitable shape, or another tf-object containing functional data.
basis	either "spline" (see tfb_spline(), the default) or "fpc" (see tfb_fpc()). (wavelet not implemented yet)
...	further arguments for tfb_spline() or tfb_fpc()

Details

tfb is a wrapper for functions that set up spline-, principal component- or wavelet-based representations of functional data. For all three, the input data $x_i(t)$ are represented as weighted sums of a set of common basis functions $B_k(t); k = 1,\dots, K$ identical for all observations and weight or coefficient vectors $b_i = (b_{i1}, \dots, b_{iK})$ estimated for each observation: $x_i(t) \approx \sum_k B_k(t) b_{ik}$. Depending on the value of basis, the basis functions $B(t)$ will either be spline functions or the first few estimated eigenfunctions of the covariance operator of the $x(t)$ (fpc) or wavelets (wavelet).

See tfb_spline() for more details on spline basis representation (the default). See tfb_fpc() for using an functional principal component representation with an orthonormal basis estimated from the data instead.

Value

a tfb-object (or a data.frame/matrix for the conversion functions, obviously.)

See Also

Other tfb-class: fpc_wsvd(), tfb_fpc(), tfb_spline()

Other tfb-class: fpc_wsvd(), tfb_fpc(), tfb_spline()

---

Functional data in FPC-basis representation

Description

These functions perform a (functional) principal component analysis (FPCA) of the input data and return an tfb_fpc tf-object that uses the empirical eigenfunctions as basis functions for representing the data. The default ("method = fpc_wsvd") uses a (truncated) weighted SVD for complete data on a common grid and a nuclear-norm regularized (truncated) weighted SVD for partially missing data on a common grid, see fpc_wsvd(). The latter is likely to break down for high PVE and/or high amounts of missingness.

Usage

tfb_fpc(data, ...)

## S3 method for class 'data.frame'
tfb_fpc(
  data,
  id = 1,
  arg = 2,
  value = 3,
  domain = NULL,
  method = fpc_wsvd,
  ...
)

## S3 method for class 'matrix'
tfb_fpc(data, arg = NULL, domain = NULL, method = fpc_wsvd, ...)

## S3 method for class 'numeric'
tfb_fpc(data, arg = NULL, domain = NULL, method = fpc_wsvd, ...)

## S3 method for class 'tf'
tfb_fpc(data, arg = NULL, method = fpc_wsvd, ...)

## Default S3 method:
tfb_fpc(data, arg = NULL, domain = NULL, method = fpc_wsvd, ...)

Arguments

data	a matrix, data.frame or list of suitable shape, or another tf-object containing functional data.
...	arguments to the method which computes the (regularized/smoothed) FPCA - see e.g. fpc_wsvd(). Unless set by the user, uses proportion of variance explained pve = 0.995 to determine the truncation levels.
id	The name or number of the column defining which data belong to which function.
arg	numeric, or list of numerics. The evaluation grid. For the data.frame-method: the name/number of the column defining the evaluation grid. The matrix method will try to guess suitable arg-values from the column names of data if arg is not supplied. Other methods fall back on integer sequences (⁠1:<length of data>⁠) as the default if not provided.
value	The name or number of the column containing the function evaluations.
domain	range of the arg.
method	the function to use that computes eigenfunctions and scores. Defaults to fpc_wsvd(), which is quick and easy but returns completely unsmoothed eigenfunctions unlikely to be suited for noisy data. See Details.

Details

For the FPC basis, any factorization method that accepts a data.frame with columns id, arg, value containing the functional data and returns a list with eigenfunctions and FPC scores structured like the return object of fpc_wsvd() can be used for the 'method“ argument, see example below. Note that the mean function, with a fixed "score" of 1 for all functions, is used as the first basis function for all FPC bases.

Value

an object of class tfb_fpc, inheriting from tfb. The basis used by tfb_fpc is a tfd-vector containing the estimated mean and eigenfunctions.

Methods (by class)

• tfb_fpc(default): convert tfb: default method, returning prototype when data is NULL

See Also

fpc_wsvd() for FPCA options.

Other tfb-class: fpc_wsvd(), tfb, tfb_spline()

Other tfb_fpc-class: fpc_wsvd()

Examples

set.seed(13121)
x <- tf_rgp(25, nugget = .02)
x_pc <- tfb_fpc(x, pve = .9)
x_pc
plot(x, lwd = 3)
lines(x_pc, col = 2, lty = 2)
x_pc_full <- tfb_fpc(x, pve = .995)
x_pc_full
lines(x_pc_full, col = 3, lty = 2)
# partially missing data on common grid:
x_mis <- x |> tf_sparsify(dropout = .05)
x_pc_mis <- tfb_fpc(x_mis, pve = .9)
x_pc_mis
plot(x_mis, lwd = 3)
lines(x_pc_mis, col = 4, lty = 2)
# extract FPC basis --
# first "eigenvector" in black is (always) the mean function
x_pc |> tf_basis(as_tfd = TRUE) |> plot(col = 1:5)

# Apply FPCA for sparse, irregular data using refund::fpca.sc:
set.seed(99290)
# create small, sparse, irregular data:
x_irreg <- x[1:8] |>
  tf_jiggle() |> tf_sparsify(dropout = 0.3)
plot(x_irreg)
x_df <- x_irreg |>
  as.data.frame(unnest = TRUE)
# wrap refund::fpca_sc for use as FPCA method in tfb_fpc --
# 1. define scoring function (simple weighted LS fit)
fpca_scores <- function(data_matrix, efunctions, mean, weights) {
  w_mat <- matrix(weights, ncol = length(weights), nrow = nrow(data_matrix),
                  byrow = TRUE)
  w_mat[is.na(data_matrix)] <- 0
  data_matrix[is.na(data_matrix)] <- 0
  data_wc <- t((t(data_matrix) - mean) * sqrt(t(w_mat)))
  t(qr.coef(qr(efunctions), t(data_wc) / sqrt(weights)))
}
# 2. define wrapper for fpca_sc:
fpca_sc_wrapper <- function(data, arg, pve = 0.995, ...) {
  data_mat <- tfd(data) |> as.matrix(interpolate = TRUE)
  fpca <- refund::fpca.sc(
    Y = data_mat, argvals = attr(data_mat, "arg"), pve = pve, ...
  )
  c(fpca[c("mu", "efunctions", "scores", "npc")],
    scoring_function = fpca_scores)
}
x_pc <- tfb_fpc(x_df, method = fpca_sc_wrapper)
lines(x_pc, col = 2, lty = 2)

---

Spline-based representation of functional data

Description

Represent curves as a weighted sum of spline basis functions.

Usage

tfb_spline(data, ...)

## S3 method for class 'data.frame'
tfb_spline(
  data,
  id = 1,
  arg = 2,
  value = 3,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

## S3 method for class 'matrix'
tfb_spline(
  data,
  arg = NULL,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

## S3 method for class 'numeric'
tfb_spline(
  data,
  arg = NULL,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

## S3 method for class 'list'
tfb_spline(
  data,
  arg = NULL,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

## S3 method for class 'tfd'
tfb_spline(
  data,
  arg = NULL,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

## S3 method for class 'tfb'
tfb_spline(
  data,
  arg = NULL,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

## Default S3 method:
tfb_spline(
  data,
  arg = NULL,
  domain = NULL,
  penalized = TRUE,
  global = FALSE,
  verbose = TRUE,
  ...
)

Arguments

data	a matrix, data.frame or list of suitable shape, or another tf-object containing functional data.
...	arguments to the calls to mgcv::s() setting up the basis (and to mgcv::magic() or mgcv::gam.fit() if penalized = TRUE). Uses k = 25 cubic regression spline basis functions (bs = "cr") by default, but should be set appropriately by the user. See Details and examples in the vignettes.
id	The name or number of the column defining which data belong to which function.
arg	numeric, or list of numerics. The evaluation grid. For the data.frame-method: the name/number of the column defining the evaluation grid. The matrix method will try to guess suitable arg-values from the column names of data if arg is not supplied. Other methods fall back on integer sequences (⁠1:<length of data>⁠) as the default if not provided.
value	The name or number of the column containing the function evaluations.
domain	range of the arg.
penalized	TRUE (default) estimates regularized/penalized basis coefficients via mgcv::magic() or mgcv::gam.fit(), FALSE yields ordinary least squares / ML estimates for basis coefficients. FALSE is much faster but will overfit for noisy data if k is (too) large.
global	Defaults to FALSE. If TRUE and penalized = TRUE, all functions share the same smoothing parameter (see Details).
verbose	TRUE (default) outputs statistics about the fit achieved by the basis and other diagnostic messages.

Details

The basis to be used is set up via a call to mgcv::s() and all the spline bases discussed in mgcv::smooth.terms() are available, in principle. Depending on the value of the penalized- and global-flags, the coefficient vectors for each observation are then estimated via fitting a GAM (separately for each observation, if !global) via mgcv::magic() (least square error, the default) or mgcv::gam() (if a family argument was supplied) or unpenalized least squares / maximum likelihood.

After the "smoothed" representation is computed, the amount of smoothing that was performed is reported in terms of the "percentage of variability preserved", which is the variance (or the explained deviance, in the general case if family was specified) of the smoothed function values divided by the variance of the original values (the null deviance, in the general case). Reporting can be switched off with verbose = FALSE.

The ... arguments supplies arguments to both the spline basis (via mgcv::s()) and the estimation (via mgcv::magic() or mgcv::gam()), the most important arguments are:

• k: how many basis functions should the spline basis use, default is 25.

• bs: which type of spline basis should be used, the default is cubic regression splines (bs = "cr")

• family argument: use this if minimizing squared errors is not a reasonable criterion for the representation accuracy (see mgcv::family.mgcv() for what's available) and/or if function values are restricted to be e.g. positive (family = Gamma()/tw()/...), in $[0,1]$ (family = betar()), etc.

• sp: numeric value for the smoothness penalty weight, for manually setting the amount of smoothing for all curves, see mgcv::s(). This (drastically) reduces computation time. Defaults to -1, i.e., automatic optimization of sp using mgcv::magic() (LS fits) or mgcv::gam() (GLM), source code in R/tfb-spline-utils.R.

If global == TRUE, this uses a small subset of curves (10⁠%⁠ of curves, at least 5, at most 100; non-random sample using every j-th curve in the data) on which smoothing parameters per curve are estimated and then takes the mean of the log smoothing parameter of those as sp for all curves. This is much faster than optimizing for each curve on large data sets. For very sparse or noisy curves, estimating a common smoothing parameter based on the data for all curves simultaneously is likely to yield better results, this is not what's implemented here.

Value

a tfb-object

Methods (by class)

• tfb_spline(data.frame): convert data frames

• tfb_spline(matrix): convert matrices

• tfb_spline(numeric): convert matrices

• tfb_spline(list): convert lists

• tfb_spline(tfd): convert tfd (raw functional data)

• tfb_spline(tfb): convert tfb: modify basis representation, smoothing.

• tfb_spline(default): convert tfb: default method, returning prototype when data is missing

See Also

mgcv::smooth.terms() for spline basis options.

Other tfb-class: fpc_wsvd(), tfb, tfb_fpc()

---

Accessing, evaluating, subsetting and subassigning tf vectors

Description

These functions access, subset, replace and evaluate tf objects. For more information on creating tf objects and converting them to/from list, data.frame or matrix, see tfd() and tfb(). See Details.

Usage

## S3 method for class 'tf'
x[i, j, interpolate = TRUE, matrix = TRUE]

## S3 replacement method for class 'tf'
x[i] <- value

Arguments

x	an tf
i	index of the observations (integerish, character or logical, usual R rules apply)
j	The arg used to evaluate the functions. A (list of) numeric vectors. NOT interpreted as a column number but as the argument value of the respective functional datum.
interpolate	should functions be evaluated (i.e., inter-/extrapolated) for values in arg for which no original data is available? Only relevant for the raw data class tfd, for which it defaults to TRUE. Basis-represented tfb are always "interpolated".
matrix	should the result be returned as a matrix or as a list of data.frames? If TRUE, j has to be a (list of a) single vector of arg. See return value.
value	tf object for subassignment. This is typed more strictly than concatenation: subassignment only happens if the common type of value and x is the same as the type of x, so subassignment never changes the type of x but may do a potentially lossy cast of value to the type of x (with a warning).

Details

Note that these break certain (terrible) R conventions for vector-like objects:

• no argument recycling,

• no indexing with NA,

• no indexing with names not present in x,

• no indexing with integers ⁠> length(x)⁠

All of the above will trigger errors.

Value

If j is missing, a subset of the functions in x as given by i.
If j is given and matrix == TRUE, a numeric matrix of function evaluations in which each row represents one function and each column represents one argval as given in argument j, with an attribute arg=j and row- and column-names derived from x[i] and j.
If j is given and matrix == FALSE, a list of tbl_dfs with columns arg = j and value = evaluations at j for each observation in i.

Examples

x <- 1:3 * tfd(data = 0:10, arg = 0:10)
plot(x)
# this operator's 2nd argument is quite overloaded -- you can:
# 1. simply extract elements from the vector if no second arg is given:
x[1]
x[c(TRUE, FALSE, FALSE)]
x[-(2:3)]
# 2. use the second argument and optional additional arguments to
#    extract specific function evaluations in a number of formats:
x[1:2, c(4.5, 9)] # returns a matrix of function evaluations
x[1:2, c(4.5, 9), interpolate = FALSE] # NA for arg-values not in the original data
x[-3, seq(1, 9, by = 2), matrix = FALSE] # list of data.frames for each function
# in order to evaluate a set of observed functions on a new grid and
# save them as a functional data vector again, use `tfd` or `tfb` instead:
tfd(x, arg = seq(0, 10, by = 0.01))

---

Constructors for vectors of "raw" functional data

Description

Various constructor methods for tfd-objects.

tfd.matrix accepts a numeric matrix with one function per row (!). If arg is not provided, it tries to guess arg from the column names and falls back on 1:ncol(data) if that fails.

tfd.data.frame uses the first 3 columns of data for function information by default: (id, arg, value)

tfd.list accepts a list of vectors of identical lengths containing evaluations or a list of 2-column matrices/data.frames with arg in the first and evaluations in the second column

tfd.default returns class prototype when argument to tfd() is NULL or not a recognised class

Usage

tfd(data, ...)

## S3 method for class 'matrix'
tfd(data, arg = NULL, domain = NULL, evaluator = tf_approx_linear, ...)

## S3 method for class 'numeric'
tfd(data, arg = NULL, domain = NULL, evaluator = tf_approx_linear, ...)

## S3 method for class 'data.frame'
tfd(
  data,
  id = 1,
  arg = 2,
  value = 3,
  domain = NULL,
  evaluator = tf_approx_linear,
  ...
)

## S3 method for class 'list'
tfd(data, arg = NULL, domain = NULL, evaluator = tf_approx_linear, ...)

## S3 method for class 'tf'
tfd(data, arg = NULL, domain = NULL, evaluator = NULL, ...)

## Default S3 method:
tfd(data, arg = NULL, domain = NULL, evaluator = tf_approx_linear, ...)

as.tfd(data, ...)

as.tfd_irreg(data, ...)

Arguments

data	a matrix, data.frame or list of suitable shape, or another tf-object. when this argument is NULL (i.e. when calling tfd()) this returns a prototype of class tfd
...	not used in tfd, except for tfd.tf – specify arg and ìnterpolate = TRUE to turn an irregular tfd into a regular one, see examples.
arg	numeric, or list of numerics. The evaluation grid. For the data.frame-method: the name/number of the column defining the evaluation grid. The matrix method will try to guess suitable arg-values from the column names of data if arg is not supplied. Other methods fall back on integer sequences (⁠1:<length of data>⁠) as the default if not provided.
domain	range of the arg.
evaluator	a function accepting arguments ⁠x, arg, evaluations⁠. See details for tfd().
id	The name or number of the column defining which data belong to which function.
value	The name or number of the column containing the function evaluations.

Details

evaluator: must be the (quoted or bare) name of a function with signature ⁠function(x, arg, evaluations)⁠ that returns the functions' (approximated/interpolated) values at locations x based on the function evaluations available at locations arg.
Available evaluator-functions:

• tf_approx_linear for linear interpolation without extrapolation (i.e., zoo::na.approx() with na.rm = FALSE) – this is the default,

• tf_approx_spline for cubic spline interpolation, (i.e., zoo::na.spline() with na.rm = FALSE),

• tf_approx_fill_extend for linear interpolation and constant extrapolation (i.e., zoo::na.fill() with fill = "extend")

• tf_approx_locf for "last observation carried forward" (i.e., zoo::na.locf() with na.rm = FALSE and

• tf_approx_nocb for "next observation carried backward" (i.e., zoo::na.locf() with ⁠na.rm = FALSE, fromLast = TRUE⁠). See tf:::zoo_wrapper and tf:::tf_approx_linear, which is simply zoo_wrapper(zoo::na.tf_approx, na.rm = FALSE), for examples of implementations of this.

Value

an tfd-object (or a data.frame/matrix for the conversion functions, obviously.)

Examples

# turn irregular to regular tfd by evaluating on a common grid:

f <- c(
  tf_rgp(1, arg = seq(0, 1, length.out = 11)),
  tf_rgp(1, arg = seq(0, 1, length.out = 21))
)
tfd(f, arg = seq(0, 1, length.out = 21))

set.seed(1213)
f <- tf_rgp(3, arg = seq(0, 1, length.out = 51)) |> tf_sparsify(0.9)
# does not yield regular data because linear extrapolation yields NAs
#   outside observed range:
tfd(f, arg = seq(0, 1, length.out = 101))
# this "works" (but may not yield sensible values..!!) for
#   e.g. constant extrapolation:
tfd(f, evaluator = tf_approx_fill_extend, arg = seq(0, 1, length.out = 101))
plot(f, col = 2)
tfd(f,
  arg = seq(0, 1, length.out = 151), evaluator = tf_approx_fill_extend
) |> lines()

---

Functions that summarize tf objects across argument values

Description

These will return a tf object containing the respective functional statistic. See tf_fwise() for scalar summaries (e.g. tf_fmean for means, tf_fmax for max. values) of each entry in a tf-vector.

Usage

## S3 method for class 'tf'
mean(x, ...)

## S3 method for class 'tf'
median(x, na.rm = FALSE, depth = c("MBD", "pointwise"), ...)

sd(x, na.rm = FALSE)

## Default S3 method:
sd(x, na.rm = FALSE)

## S3 method for class 'tf'
sd(x, na.rm = FALSE)

var(x, y = NULL, na.rm = FALSE, use)

## Default S3 method:
var(x, y = NULL, na.rm = FALSE, use)

## S3 method for class 'tf'
var(x, y = NULL, na.rm = FALSE, use)

## S3 method for class 'tf'
summary(object, ...)

Arguments

x	a tf object
...	optional additional arguments.
na.rm	logical. Should missing values be removed?
depth	method used to determine the most central element in x, i.e., the median. One of the functional data depths available via tf_depth() or "pointwise" for a pointwise median function.
y	NULL (default) or a vector, matrix or data frame with compatible dimensions to x. The default is equivalent to y = x (but more efficient).
use	an optional character string giving a method for computing covariances in the presence of missing values. This must be (an abbreviation of) one of the strings "everything", "all.obs", "complete.obs", "na.or.complete", or "pairwise.complete.obs".
object	a tfd object

Value

a tf object with the computed result.
summary.tf returns a tf-vector with the mean function, the variance function, the functional median, and the functional range (i.e., pointwise min/max) of the central half of the functions, as defined by tf_depth().

See Also

tf_fwise()

Other tidyfun summary functions: functionwise

---

Make syntactically valid unique names

Description

See above.

Usage

unique_id(x)

Arguments

x

any input

Value

x turned into a list.

See Also

Other tidyfun developer tools: ensure_list(), prep_plotting_arg()

---

vctrs methods for tf objects

Description

These functions are the extensions that allow tf vectors to work with vctrs.

Usage

## S3 method for class 'tfd_reg'
vec_cast(x, to, ...)

## S3 method for class 'tfd_irreg'
vec_cast(x, to, ...)

## S3 method for class 'tfd_reg'
vec_cast.tfd_reg(x, to, ...)

## S3 method for class 'tfd_irreg'
vec_cast.tfd_reg(x, to, ...)

## S3 method for class 'tfb_spline'
vec_cast.tfd_reg(x, to, ...)

## S3 method for class 'tfb_fpc'
vec_cast.tfd_reg(x, to, ...)

## S3 method for class 'tfd_reg'
vec_cast.tfd_irreg(x, to, ...)

## S3 method for class 'tfd_irreg'
vec_cast.tfd_irreg(x, to, ...)

## S3 method for class 'tfb_spline'
vec_cast.tfd_irreg(x, to, ...)

## S3 method for class 'tfb_fpc'
vec_cast.tfd_irreg(x, to, ...)

## S3 method for class 'tfb_spline'
vec_cast(x, to, ...)

## S3 method for class 'tfb_fpc'
vec_cast(x, to, ...)

## S3 method for class 'tfb_spline'
vec_cast.tfb_spline(x, to, ...)

## S3 method for class 'tfb_fpc'
vec_cast.tfb_spline(x, to, ...)

## S3 method for class 'tfb_spline'
vec_cast.tfb_fpc(x, to, ...)

## S3 method for class 'tfb_fpc'
vec_cast.tfb_fpc(x, to, ...)

## S3 method for class 'tfd_reg'
vec_cast.tfb_spline(x, to, ...)

## S3 method for class 'tfd_irreg'
vec_cast.tfb_spline(x, to, ...)

## S3 method for class 'tfd_reg'
vec_cast.tfb_fpc(x, to, ...)

## S3 method for class 'tfd_irreg'
vec_cast.tfb_fpc(x, to, ...)

## S3 method for class 'tfd_reg'
vec_ptype2(x, y, ...)

## S3 method for class 'tfd_reg'
vec_ptype2.tfd_reg(x, y, ...)

## S3 method for class 'tfd_irreg'
vec_ptype2.tfd_reg(x, y, ...)

## S3 method for class 'tfb_spline'
vec_ptype2.tfd_reg(x, y, ...)

## S3 method for class 'tfb_fpc'
vec_ptype2.tfd_reg(x, y, ...)

## S3 method for class 'tfd_irreg'
vec_ptype2(x, y, ...)

## S3 method for class 'tfd_reg'
vec_ptype2.tfd_irreg(x, y, ...)

## S3 method for class 'tfd_irreg'
vec_ptype2.tfd_irreg(x, y, ...)

## S3 method for class 'tfb_spline'
vec_ptype2.tfd_irreg(x, y, ...)

## S3 method for class 'tfb_fpc'
vec_ptype2.tfd_irreg(x, y, ...)

## S3 method for class 'tfb_spline'
vec_ptype2(x, y, ...)

## S3 method for class 'tfb_spline'
vec_ptype2.tfb_spline(x, y, ...)

## S3 method for class 'tfb_fpc'
vec_ptype2.tfb_spline(x, y, ...)

## S3 method for class 'tfd_reg'
vec_ptype2.tfb_spline(x, y, ...)

## S3 method for class 'tfd_irreg'
vec_ptype2.tfb_spline(x, y, ...)

## S3 method for class 'tfb_fpc'
vec_ptype2(x, y, ...)

## S3 method for class 'tfb_spline'
vec_ptype2.tfb_fpc(x, y, ...)

## S3 method for class 'tfb_fpc'
vec_ptype2.tfb_fpc(x, y, ...)

## S3 method for class 'tfd_reg'
vec_ptype2.tfb_fpc(x, y, ...)

## S3 method for class 'tfd_irreg'
vec_ptype2.tfb_fpc(x, y, ...)

Arguments

x	Vectors to cast.
to	Type to cast to. If NULL, x will be returned as is.
...	For vec_cast_common(), vectors to cast. For vec_cast(), vec_cast_default(), and vec_restore(), these dots are only for future extensions and should be empty.
y	Vectors to cast.

Details

Notes on vec_cast: Use tf_rebase() to change the representations of tf-vectors, these methods are only for internal use – automatic/implicit casting of tf objects is tricky because it's hard to determine automatically whether such an operation would lose precision (different bases with different expressivity? different argument grids?), and it's not generally clear which instances of which tf-subclasses should be considered the "richer" objects. Rules for casting:

• If the casted object's domain would not contain the entire original domain, no casting is possible (would lose data).

• Every cast that evaluates (basis) functions on different arg values is a lossy cast, since it might lose precision (vctrs::maybe_lossy_cast).

• As long as the casted object's domain contains the entire original domain:

  • every tfd_reg, tfd_irreg or tfb can always be cast into an equivalent tfd_irreg (which may also change its evaluator and domain).

  • every tfd_reg can always be cast to tfd_reg (which may change its evaluator and domain)

  • every tfb can be cast losslessly to tfd (regular or irregular, note it's lossless only on the original arg-grid)

• Any cast of a tfd into tfb is potentially lossy (because we don't know how expressive the chosen basis is)

• Only tfb with identical bases and domains can be cast into one another losslessly

Value

for vec_cast: the casted tf-vector, for vec_ptype2: the common prototype

See Also

vctrs::vec_cast(), vctrs::vec_ptype2()

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