# [Numpy-discussion] build numpy matrix out of smaller matrix

eat e.antero.tammi at gmail.com
Thu Dec 1 13:41:16 EST 2011

```Oops, slightly incorrect answer, but anyway my intention was more along the
lines:
In []: a= np.array([[1, 2], [3, 4]])
In []: np.c_[[a, a], [a, a]].reshape(4, 4)
Out[]:
array([[1, 2, 1, 2],
[3, 4, 3, 4],
[1, 2, 1, 2],
[3, 4, 3, 4]])

On Thu, Dec 1, 2011 at 8:16 PM, <josef.pktd at gmail.com> wrote:

> On Thu, Dec 1, 2011 at 12:26 PM, Benjamin Root <ben.root at ou.edu> wrote:
> > On Thu, Dec 1, 2011 at 10:52 AM, jonasr <jonas.ruebsam at web.de> wrote:
> >>
> >>
> >> Hi,
> >> is there any possibility to define a numpy matrix, via a smaller given
> >> matrix, i.e. in matlab
> >> i can do this like
> >>
> >> a=[1 2 ; 3 4 ]
> >>
> >>
> >> A=[a a ; a a ]
> >>
> >> so that i finally get
> >>
> >> A=[ [1,2,1,2]
> >>      [3,4,3,4]
> >>      [1,2,1,2]
> >>      [3,4,3,4]]
> >>
> >> i tried different things on numpy which didn't work
> >> any ideas ?
> >>
> >> thank you
> >>
> >
> > numpy.tile() might be what you are looking for.
>
> or which is my favorite tile and repeat replacement
>
> >>> a= np.array([[1, 2], [3, 4]])
> >>> np.kron(np.ones((2,2)), a)
> array([[ 1.,  2.,  1.,  2.],
>       [ 3.,  4.,  3.,  4.],
>       [ 1.,  2.,  1.,  2.],
>       [ 3.,  4.,  3.,  4.]])
>
> >>> np.kron(a, np.ones((2,2)))
> array([[ 1.,  1.,  2.,  2.],
>       [ 1.,  1.,  2.,  2.],
>       [ 3.,  3.,  4.,  4.],
>       [ 3.,  3.,  4.,  4.]])
>
But, of'course this is way more generic (and preferable) approach to
utilize.

eat

>
> Josef
>
> >
> > Cheers!
> > Ben Root
> >
> >
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> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
> >
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