How can I use interp2 or interp3 for data without using MESHGRID or NGRID previously?

I have coordinates X, Y, Z each of one is a Matrix of 67 x 147. Each Matrix was no generated by MESHGRID or NGRID method but just were adjusted by means reshape() to be visualize with surf(). However when I try to use interp2() to get a value that I need. There is a error that indicates that data were not generated with meshgrid(). How can I convert the data to interpolate?.

Best Regards

Diego F.

Answer 1

[Walter Roberson]

Interpolation for 2-D gridded data in meshgrid format

ZI = interp2(X,Y,Z,XI,YI) returns matrix ZI containing elements corresponding to the elements of XI and YI and determined by interpolation within the two-dimensional function specified by matrices X, Y, and Z. X and Y must be monotonic, and have the same format ("plaid") as if they were produced by meshgrid.

Are your X and Y matrices monotonic and "plaid" ? So one of them goes like

1 2 3
1 2 3
1 2 3

and the the other one goes like

4 4 4
5 5 5
6 6 6

?

[Diego Flores]

Hi Walter, thanks for the answer.

The Matrices are monotonic but they are not "plaid".

 X=0.1216967163 0.1216976461 0.1216987718   ...   ...
   0.1217044517 0.1217053814 0.1217065067   ...   ...
   0.1217115548 0.1217124842 0.1217136092   ...   ...
        ...          ...          ...
        ...          ...          ...

Y=0.00358609375 0.00358599648 0.003585879951   ...   ...
  0.003313193137 0.00331309534 0.00331297815   ...   ...
  0.003041094743 0.00304099621 0.003040878105  ...   ...
       ....          ....           ....
       ....          ....           ....

I think the "plaid" matrices just work for simple examples, but in real problems the matrices are not "plaid" and interpolation methods available in MATLAB fail.

I hope there is a solution

Thanks in advance

Diego

[Walter Roberson]

Consider using http://www.mathworks.com/help/matlab/ref/triscatteredinterp.html or in newer versions http://www.mathworks.com/help/matlab/ref/scatteredinterpolantclass.html