# Alternative Methods for Interpolation or Solutions of Interpolation Errors

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Volkan Yangin on 6 Dec 2015
Commented: John D'Errico on 7 Dec 2015
Hi everbody.
Sometimes i give an error when making interpolation process for ex. "The values of X should be distinct error".
I have an exam this tuesday which will be done by matlab. And i am afraid of interpolation errors.
What are the alternative methods for interpolation or solutions of errors like "The values of X should be distinct" etc.?
Thanks a lot.
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### Answers (2)

Walter Roberson on 7 Dec 2015
The available techniques depend a great deal upon whether the Y corresponding to the duplicate X are the same or different.
If the Y values are the same then the major technique is to unique() the X values and take the corresponding Y values. One way of doing that is to use
XY = [X(:), Y(:)];
uXY = unique(XY,'rows');
uX = uXY(:,1);
uY = uXY(:,2);
interp1(uX, uY, locations_to_interpolate_at)
But typically one would instead construct the X values to be unique.
What are some circumstances under which you have had difficulty with duplicate X values?
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Volkan Yangin on 7 Dec 2015
Thanks Walter Roberson for your answer.
For ex. my X values = [8.79 9.42 10.05 ...], these values are increasing but through to 900. column, X values decreasing to 0. My Y values haven't got standart tendency, for ex. [970 971 2394 972 ...]. When i use the interp1 command for ex. interp1(X,Y,25.45) etc, i encounter this error. I have some duplicate values of X but not Y.
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John D'Errico on 7 Dec 2015
Please do not add answers every time you wish to comment. Use the COMMENTS!!!!!!!!

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