Question

I want to mark all maxima along a given axis of an array (which shape may be n-dimensional), this works fine along the first one, but for the rest I can’t figure it out. I don’t want to iterate over axis, because there can be arbritarily many of them.

>>> A = range(5)*3
>>> A = array(a).reshape([3,5], order='F')
>>> A
array([[0, 3, 1, 4, 2],
       [1, 4, 2, 0, 3],
       [2, 0, 3, 1, 4]])
>>> B = amax(A, axis= 0)
>>> C = amax(A, axis= 1)
>>> B == A
array([[False, False, False,  True, False],
       [False,  True, False, False, False],
       [ True, False,  True, False,  True]], dtype=bool)

This is what I want it to do for:

>>> C == A
False

but (of course) it does not.

How to get this working?

Answer 1

I finally came up with:

def tiletuple(t,axis):
  m = [1]*t.ndim
  m[axis] = t.shape[axis]
  return m

ax = 1
tile(expand_dims(amax(A, axis=ax), axis=ax), tiletuple(A, ax)) == A