MATLAB: Interpolating a function that is constant over some parts of its domain

constant functioninterp1interpolation

I'm trying to write code that will linearly interpolate samples from a generic real-valued function. Interp1 seems to break if the function is constant over any part of its domain, and unfortunately for me this is an extremely common use case – as a simple function:
       {0, if x<0
f(x) = {x, if 0<=x<=1
       {1, otherwise
It seems like interp1([0, 0, 1, 1], [-10,0,1,10], x) ought to return this function (for x \in [-10,10]), but instead I get the error that "The grid vectors must contain unique points."
Is there another interpolation function that doesn't break when you feed it functions that are sometimes constant?

Best Answer

Hi Jonathan,
just swap inputs,
interp1([-10,0,1,10], [0,0,1,1], x)
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