approx_circular: "Linearly" interpolates angles along a circle

In jiho/discr: Drifting In Situ Chamber User Software in R

Description

Interpolate angles by converting them to cardinal coordinates, linearly interpolating positions in cardinal space (x, y) and converting the resulting points back into polar space (i.e. angles). Please note that this will not work for steps of angles >= pi in the input vector of angles; but this is very difficult to check in a general way so no check is made

Usage

approx_circular(x, angles, xout, ...)

Arguments

x	"coordinate" (e.g. time of measurement) of the angles to be interpolated
angles	angles to be interpolated, of class circular or in trigonometric reference
xout	"coordinates" where the interpolation should take place
...	passed to approx

Value

A list with components x, containing the output coordinate (xout), and y, containing the interpolated angles (in the same circular reference as the input angles)

Examples

x <- c(0, 1)
y <- c(0, pi/2)
approx_circular(x=x, angles=y, xout=c(0, .5, 1))

library("circular")
y <- circular(c(0, 90), template="geographics", units="degrees")
approx_circular(x=x, angles=y, xout=c(0, .5, 1))

# this works
x <- c(0, 1, 2)
y <- c(0, 0.7*pi, 1.5*pi)
approx_circular(x=x, angles=y, xout=c(0, .5, 1, 1.5, 2))

# but gives incorrect results because one step is larger than pi
y <- c(0, 0.4*pi, 1.5*pi)
approx_circular(x=x, angles=y, xout=c(0, .5, 1, 1.5, 2))
y <- c(1.5*pi, 0.6*pi, 0.7*pi)
approx_circular(x=x, angles=y, xout=c(0, .5, 1, 1.5, 2))

jiho/discr documentation built on May 19, 2019, 9:30 a.m.