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

josef.pktd at gmail.com josef.pktd at gmail.com
Thu Dec 1 13:16:15 EST 2011


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.]])

Josef

>
> Cheers!
> Ben Root
>
>
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