Returns the Chebyshev interpolation of a sampled function. Chebyshev interpolation is useful for accurately interpolating a smooth function using a very small number of samples. The key requirement for this type of interpolation to work is that the function is sampled on the Chebyshev roots grid.
Interpolates the function f onto the xi points. It assumes that f contains the samples of the function taken on the Chebyshev roots grid specified in x; x must be constructed by the call
# x = chpts(xmin,xmax,NumPts), otherwise an error is returned.
See example for the chpts command.