curvature_spline: Calculate total curvature from smoothing or interpolating...

In mannfred/curvr: Calculate Total Curvature From Landmarked Specimens

Calculate total curvature from smoothing or interpolating splines.

Description

Calculate total curvature from smoothing or interpolating splines.

Usage

curvature_spline(landmark_matrix, x_range, type = "smooth")

Arguments

landmark_matrix	is a matrix object with [,1] containing the x landmark coordinates and [,2] containing the y landmark coordinates.
x_range	the lower and upper x-value bounds to calculate curvature. Concatenate the lower and upper bounds using c(), E.g. for lower = 1 and upper = 10, type c(1,10).
type	either 'ip' for an interpolating spline or 'smooth' for a smoothing spline. Uses stats::spline() or stats::smooth.spline(), respectively, for curve fitting and estimating the derivatives. Default is type = 'smooth'. See: ?spline and ?smooth.spline for details.

Value

a 'list' with two named elements. '$Ktot' is the total curvature in radians. '$Ki' is a numeric vector of local curvature values.

Examples

# a landmark matrix describing a segment of the unit circle#'
x <- seq(0, 1, by = 0.01)
y <- sqrt(1-x^2)
mdat <- matrix(c(x, y), nrow = 101, ncol = 2)

# total curvature between x=0 and x=sqrt(2)/2 should be approximately pi/4
abs(curvature_spline(mdat, c(0, sqrt(2)/2), type='smooth')$Ktot)

mannfred/curvr documentation built on Nov. 6, 2024, 7:10 p.m.