tfbrackets {tf}

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))