Inter- and extrapolation functions for tfd-objects

These are exported evaluator callbacks for tfd objects. They control how function values are inter-/extrapolated to previously unseen arg values and are used by tf_evaluate().

In typical use, set an evaluator when constructing a tfd (tfd(..., evaluator = tf_approx_linear)) or replace it later via tf_evaluator(x) <- tf_approx_none.

These helpers are wrappers around zoo::na.fill(), zoo::na.approx(), etc. and all share the same signature (x, arg, evaluations), so they can also be called directly.

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)

• 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()

Examples

x <- tfd(matrix(c(0, 1), nrow = 1), arg = c(0, 1))
tf_evaluate(x, c(0, 0.5, 1))
#> [[1]]
#> [1] 0.0 0.5 1.0
#> 
tf_evaluator(x) <- tf_approx_none
tf_evaluate(x, c(0, 0.5, 1))
#> [[1]]
#> [1]  0 NA  1
#> 

tf_approx_linear(
  x = c(0, 0.5, 1),
  arg = c(0, 1),
  evaluations = c(0, 1)
)
#> [1] 0.0 0.5 1.0