How to use Matlab's interp1 with linear interpolation and clip extrapolation

1
votes

From the documentation of Matlab's interp1, it seems that the method used for interpolation and extrapolation should be the same. However, I would like to implement a linear interpolation with clip extrapolation (hold extreme values). Is this possible using the interp1 function?

1
matlabinterpolationlinear-interpolationextrapolation

1 Answers

1
votes

It looks like you can't do it directly from the interp1 function:

Extrapolation strategy, specified as the string, 'extrap', or a real scalar value.

  • Specify 'extrap' when you want interp1 to evaluate points outside the domain using the same method it uses for interpolation.
  • Specify a scalar value when you want interp1 to return a specific constant value for points outside the domain.

but I guess it's not too hard to implement yourself:

function vq = LinearInterpWithClipExtrap(x,v,xq)

    vq = interp1(x,v,xq);

    [XMax, idxVMax] = max(x);
    [XMin, idxVMin] = min(x);

    idxMax = xq > XMax;
    idxMin = xq < XMin;

    vq(idxMax) = v(idxVMax);
    vq(idxMin) = v(idxVMin);

end