| chebeval {chebpol} | R Documentation |
Given Chebyshev coefficients, evaluate the interpolation in a point.
chebeval(x, coef, intervals = NULL,
threads = getOption("chebpol.threads"))
x |
The point to evaluate. |
coef |
The Chebyshev coefficients. Typically from a call to
|
intervals |
A list of minimum and maximum values. One for each dimension of the hypercube. |
threads |
And integer. In case |
A numeric. The interpolated value.
# make a function which is known to be unsuitable for Chebyshev approximation f <- function(x) sign(x) # make a standard Chebyshev interpolation ch <- ipol(f,dims=50,method='chebyshev') # then do a truncated interpolation val <- evalongrid(f,50) coef <- chebcoef(val) # truncate the high frequencies coef[-(1:10)] <- 0 # make a truncated approximation tch <- Vectorize(function(x) chebeval(x,coef)) # make a lower degree also ch2 <- ipol(f,dims=10,method='chebyshev') # plot the functions ## Not run: s <- seq(-1,1,length.out=400) plot(s,ch(s),col='red',type='l') lines(s,tch(s),col='blue') lines(s,f(s)) lines(s,ch2(s),col='green') ## End(Not run)