chebyshev differentiation matrices codes not callable

% check the base case
if N == 0; D = 0; x = 1; return; end

% create the Chebyshev grid
x = cos(pi*(0:N)/N)';

c = [2; ones(N-1,1);2].*(-1).^(0:N)';
X = repmat(x,1,N+1);
dX = X-X';
D = (c*(1./c)')./(dX+(eye(N+1)));
D = D - diag(sum(D'));

[Walter Roberson]

Duplicated by the later https://www.mathworks.com/matlabcentral/answers/389165-chebyshev-differential-matrices-code-not-callable which appears to be more complete