Need a fix for interp1 error

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

Answer 1

[dpb]

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.

[Chris Swain-Phipps]

Yep, that did the trick.

Cheers!