[Numpy-discussion] repmat equivalent?

Albert Strasheim fullung at gmail.com
Thu Feb 23 13:23:01 CST 2006


On 2/23/06, Travis Oliphant <oliphant.travis at ieee.org> wrote:
> Albert Strasheim wrote:
> >Hello all
> >
> >I recently started using NumPy and one function that I am really
> >missing from MATLAB/Octave is repmat. This function is very useful for
> >implementing algorithms as matrix multiplications instead of for
> >loops.
> >
> >
> There is a function in scipy.linalg called kron that could be brought
> over which can do a repmat.

I quickly tried a few of my test cases with following implementation of repmat:

from numpy import asarray
from scipy.linalg import kron

def repmat(a, m, n):
   a = asarray(a)
   return kron(ones((m, n)), a)

This test:

a = repmat(1, 1, 1)
assert_equal(a, 1)

fails with:

ValueError: 0-d arrays can't be concatenated

and this test:

a = repmat(array([1,2]), 2, 3)
assert_array_equal(a, array([[1,2,1,2,1,2], [1,2,1,2,1,2]]))

fails with:

AssertionError: Arrays are not equal (shapes (12,), (2, 6) mismatch)



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