Cubic Spline Interpolation

Performs cubic spline interpolation. When spar is NULL, uses stats::spline() with the FMM method. Otherwise uses stats::smooth.spline() for smoothing.

Usage

interp_spline(x, y, xout, spar = NULL)

Arguments

x

Numeric vector of observed x-values (no duplicates, length >= 4).

y

Numeric vector of observed y-values.

xout

Numeric vector of x-values where interpolation is desired.

spar

Smoothing parameter passed to smooth.spline(). NULL for standard (non-smoothing) spline.

Value

A tibble with columns x and y. The attribute method is set to "spline" or "smooth_spline" depending on the variant used.

Examples

x = c(1, 2, 3, 4, 5)
y = c(2, 4, 1, 5, 3)
interp_spline(x, y, xout = c(1.5, 2.5, 3.5))
#> # A tibble: 3 × 2
#>       x     y
#>   <dbl> <dbl>
#> 1   1.5  4.55
#> 2   2.5  2.03
#> 3   3.5  2.59
interp_spline(x, y, xout = c(1.5, 2.5, 3.5), spar = 0.8)
#> # A tibble: 3 × 2
#>       x     y
#>   <dbl> <dbl>
#> 1   1.5  2.55
#> 2   2.5  2.85
#> 3   3.5  3.15