ifcht(V) computes the inverse Chebyshev transform of a N+1 by 1 array A. If A corresponds to the weights of a linear combination of Chebyshev polynomials, then ifcht(a) computes the dataset interpolated by A at the Chebyshev–Gauss–Lobatto points cos(pi*(0:N)/N).
Suppose A = [3; 2; 1]. Then the function
f(x) = A(1)*1 + A(2)*x + A(3)*(2*x^2 - 1)
evaluated at x = cos(pi*(0:2)/2) = [1,0,-1] is given by ifcht(A).
x = cos(pi*(0:2)/2); %create Chebyshev grid of three points
xx = linspace(-1,1); % create dense grid over domain
A = [3; 2; 1];
f = A(1)*1 + A(2)*xx + A(3)*(2*xx.^2 - 1);
matched usual naming convention
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