I have matrix a which has the shape of [100,100], and matrix b of the same shape [100,100]. They are filled with some values.
What I want to do, is to build such diagonal matrixes [[a1,0],[0,b1]] for each element of a and b.
What is the best to do this?
I belive the expected shape is then array c = [2,2,100,100], where first [2,2] represent the shape of one diagonal matrix, and in total, there are [100,100] of such arrays.
F.e. let's suppose my a = [[1,2],[3,4]], b = [[5,6],[7,8]] . What I wanna get: arr1 = [[1,0],[0,5]], array2 = [[2,0],[0,6]], and so on.. so, in total the final shape is [2,2,4,4]
Thank you!
You wrote that the final shape of your "matrix of diagonal matrices" should be (2, 2, n, n) but IMO what you really want is a (n, n, 2, 2) shape, so that you can address it using out[i,j] to obtain
[ [a[i,j], 0],
[0, b[i,j]] ]
With your possible agreement on my different understanding, here it is the code that gives yo what you want
In [64]: import numpy as np
...: n = 3 ; nn = n*n
...: a, b = np.arange(2*nn).reshape(2,n,n)
...: c = np.transpose(np.array((a,b)),(1,2,0)).reshape(n,n,2)
...: out = np.zeros((n,n,2,2))
...: out[:,:,0,0] = c[:,:,0]; out[:,:,1,1] = c[:,:,1]
...: print('2,1',a[2,1],b[2,1],out[2,1],sep='\n')
...: print('0,0',a[0,0],b[0,0],out[0,0],sep='\n')
...: print('0,2',a[0,2],b[0,2],out[0,2],sep='\n')
2,1
7
16
[[ 7. 0.]
[ 0. 16.]]
0,0
0
9
[[0. 0.]
[0. 9.]]
0,2
2
11
[[ 2. 0.]
[ 0. 11.]]
In [65]: out.shape
Out[65]: (3, 3, 2, 2)
It should be possible to generalize this procedure to an arbitrary number of rectangular N×M matrices a, b, c, ..., n, ... with a little more of brain consumption.