MATLAB: Lagrangepoly function shows me an error, why

interpolationlagrange

X = [1 2 3 4 5 6 7 8]; Y = [0 1 0 1 0 1 0 1]; [P,R,S] = lagrangepoly(X,Y);
xx = 0.5 : 0.01 : 8.5; plot(xx,polyval(P,xx),X,Y,'or',R,S,'.b',xx,spline(X,Y,xx),'–g') grid axis([0.5 8.5 -5 5])
Why do I get an ERROR? Undefined function or variable 'lagrangepoly'

Best Answer

You first need to download it from the File Exchange at Lagrange Interpolator Polynomial (link) and then install it on your MATLAB search path.
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