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

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?

[Stephen23]

The interp1 help page shows the syntax:

vq = interp1(x,v,xq)

where x is the independent variable. You have the x and v swapped around.

Answer 1

[David Goodmanson]

Hi Jonathan,

just swap inputs,

interp1([-10,0,1,10], [0,0,1,1], x)

[Jonathan Hawkins]

Oops... That's embarrassing. Thank you!