Need a fix for interp1 error

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Hi,
I am trying to use interp1() function on some input data to increase the number of data points I have available to perform more precise checks, my input data is stated to 5 d.p. but ocassionally adjacent values can be identical (i.e. 0.00007, 0.00026, 0.00041, 0.00041, 0.00057...).
Any thoughts on how I still use the interp1 function without my script crashing when identical values are present?
Many Thanks,
Chris

Accepted Answer

dpb
dpb on 27 Jun 2022
The simplest is to use
[ux,ia]=unique(x);
vi=interp1(ux,y(ia),v);
This will use the first of the y values for each unique x; you could get more sophisticated and find those values and average them or otherwise set the interpolant value at that value.
Alternatively, I have on occasion found the duplicate locations and adjusted their positions by ux+/-2*eps(ux) to make them just far enough apart that interp1 doesn't complain. This is useful if there is a real discontinuity in the interpolant at the point and it is desired to model it as well.
  1 Comment
Chris Swain-Phipps
Chris Swain-Phipps on 27 Jun 2022
Yep, that did the trick.
Cheers!

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