I tried to reproduce the result in Python from MATLAB. However, it seems I do not understand. This is the correct MATLAB code:
nx = 5; ny = 7; x = linspace(0, 1, nx); dx = x(2) - x(1); y = linspace(0, 1, ny); dy = y(2) - y(1); onex = ones(nx, 1); oney = ones(ny, 1); Dx = spdiags([onex -2*onex onex], [-1 0 1], nx, nx); Dy = spdiags([oney -2*oney oney], [-1 0 1], ny, ny); Ix = eye(nx); Iy = eye(ny); L = kron(Iy, Dx); size(L) % 35 35
Now this is the Python code:
nx = 5 ny = 7 x = linspace(0, 1, nx); dx = x[1] - x[0] y = linspace(0, 1, ny); dy = y[1] - y[0] onex = ones(nx) oney = ones(ny) Dx = sparse.dia_matrix( ([onex, -2*onex, onex], [-1,0,1] ), shape=(nx,nx)) Dy = sparse.dia_matrix( ([oney, -2*oney, oney], [-1,0,1] ), shape=(ny,ny)) Ix = eye(nx) Iy = eye(ny) L = kron(Iy, Dx) L.shape # (7, 7)
As far as I was able to verify, everything is correct, so far the definition of L. According to MATLAB kron(Iy, Dx) (which should be a kronecker product), the matrix should be 35X35, but Python believes that it should be 7X7. In simpler calculations, both give the correct answer:
Python:
kron(array(([1,2],[2,3])), [1,2]) array([[1, 2, 2, 4], [2, 4, 3, 6]])
MATLAB
kron([1 2; 2 3], [1 2]) ans = 1 2 2 4 2 4 3 6
Why am I getting different results?
Thanks!