Shift matrix such that given location in centered

Question

You are given an nxn ndarray M and location (x, y) and the goal is to shift the values such that c = (x, y) is centered. Values that "fall outside" are removed and empty space is filled with zeros.

Example:

Is there any function for it in numpy/scipy or any other packages in python?

Thank you

For second output, do you mean `c=(3,4)`? In any case, I don't think there would be a function specifically for this. Happy to be proven wrong, of course. — Quang Hoang, Feb 23 '21 at 02:17
This looks related: https://stackoverflow.com/questions/30399534/shift-elements-in-a-numpy-array — xdhmoore, Feb 23 '21 at 02:22

Alain T. · Accepted Answer · 2021-02-23T04:30:48.363

I don't know of a numpy function that does that directly, but you can easily write one:

def shift(M,c,r):
    w,h = M.shape
    return np.pad(M,((w,w),(h,h)),'constant')[w//2+1+c:,h//2+1+r:][:w,:h]

output:

m = np.arange(1,6)[:,None]*np.ones(5).astype(np.int)
print(m)

[[1 1 1 1 1]
 [2 2 2 2 2]
 [3 3 3 3 3]
 [4 4 4 4 4]
 [5 5 5 5 5]]


print(shift(m,0,0))

[[0 0 0 0 0]
 [0 0 0 0 0]
 [0 0 1 1 1]
 [0 0 2 2 2]
 [0 0 3 3 3]]

print(shift(m,3,4))

[[2 2 2 0 0]
 [3 3 3 0 0]
 [4 4 4 0 0]
 [5 5 5 0 0]
 [0 0 0 0 0]]

Shift matrix such that given location in centered

1 Answers1