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def sub2ind(array_shape, rows, cols):
ind = rows*array_shape[1] + cols
ind[ind < 0] = -1
ind[ind >= array_shape[0]*array_shape[1]] = -1
return ind
def ind2sub(array_shape, ind):
ind[ind < 0] = -1
ind[ind >= array_shape[0]*array_shape[1]] = -1
rows = (ind.astype('int') / array_shape[1])
cols = ind % array_shape[1]
return (rows, cols)