circleVertices: Generate vertex coordinates for a circle
Description
Generates vertex coordinates for a circle given its centre coordinates
and radius.
Usage
circleVertices(xc, yc, radius, npoints = 25)
Arguments
xc
Circle centre X ordinate.
yc
Circle centre Y ordinate.
npoints
Number of distinct vertices required.
Value
A 2-column matrix of X and Y values. The final row is a copy
of the first row to create a closed polygon, so the matrix has
npoints + 1 rows.