Python numpy: create 2d array of values based on coordinates

Question

I have a file containing 3 columns, where the first two are coordinates (x,y) and the third is a value (z) corresponding to that position. Here\'s a short example:

Answer 1

If you have scipy installed, you could take advantage of its sparse matrix module. Get the values from the text file with genfromtxt, and plug those 'columns' directly into a sparse matrix creator.

In [545]: txt=b"""x y z
0 1 14
0 2 17
1 0 15
1 1 16
2 1 18
2 2 13
"""

In [546]: xyz=np.genfromtxt(txt.splitlines(),names=True,dtype=int)

In [547]: sparse.coo_matrix((xyz['z'],(xyz['y'],xyz['x']))).A     
Out[547]: 
array([[ 0, 15,  0],
       [14, 16, 18],
       [17,  0, 13]])

But Joe's z_array=np.zeros((3,3),int); z_array[xyz['y'],xyz['x']]=xyz['z'] is considerably faster.