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My aim is to interpolate some data. To do that i have to create a meshgrid. To do this step, i got an array with my 2D coordinate "coord" (first column : element number, second : X and third : Y).

I do a meshgrid with np.meshgrid as you can see below. But my results seem to be strange, so i would like to know if i have done a mistake...Must i have to reorganize my data before meshgrid step?

import numpy as np
coord = np.array([[  1.        ,  -1.38888667,  -1.94444333],
       [  2.        ,  -1.94444333,  -1.38888667],
       [  3.        ,   0.27777667,  -1.94444333],
       [  4.        ,  -0.27777667,  -1.38888667],
       [  5.        ,   1.94444333,  -1.94444333],
       [  6.        ,   1.38888667,  -1.38888667],
       [  7.        ,  -1.38888667,  -0.27777667],
       [  8.        ,  -1.94444333,   0.27777667],
       [  9.        ,   0.27777667,  -0.27777667],
       [ 10.        ,  -0.27777667,   0.27777667],
       [ 11.        ,   1.94444333,  -0.27777667],
       [ 12.        ,   1.38888667,   0.27777667],
       [ 13.        ,  -1.38888667,   1.38888667],
       [ 14.        ,  -1.94444333,   1.94444333],
       [ 15.        ,   0.27777667,   1.38888667],
       [ 16.        ,  -0.27777667,   1.94444333],
       [ 17.        ,   1.94444333,   1.38888667],
       [ 18.        ,   1.38888667,   1.94444333]])

[Y,X]=np.meshgrid(coord[:,2],coord[:,1])

If i plot Y, i got that : 

plt.imshow(Y);plt.colorbar();plt.show()

enter image description here

---- EDIT LATER -----

I m wondering (for example) if the coordinates with meshgrid have to be strictly increasing? if there is a better way when i have some coordinates not organized?

For the interpolation, i would like to use :

def interpolate(values, tri,uv,d=2):
    simplex = tri.find_simplex(uv)
    vertices = np.take(tri.simplices, simplex, axis=0)
    temp = np.take(tri.transform, simplex, axis=0)
    delta = uv- temp[:, d]
    bary = np.einsum('njk,nk->nj', temp[:, :d, :], delta)  
    return np.einsum('nj,nj->n', np.take(values, vertices),  np.hstack((bary, 1.0 - bary.sum(axis=1, keepdims=True))))

which was used in Stack before Speedup scipy griddata for multiple interpolations between two irregular grids allowing to limit the calculation time

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  • What do you mean by "strange"? – Lee Nov 16 '15 at 09:21
  • I m wondering (for example) if the coordinates with meshgrid have to be strictly increasing? – user3601754 Nov 16 '15 at 09:23
  • what data are you using for the interpolation? as for the X,Y sorting requirement, it is not explicit, but implicit since they are to be used to represent the axes...but can it be assumed that you tried sorting and the results were unsatisfactory? –  Nov 16 '15 at 09:36

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