# [SciPy-user] Type handling of matrices

Gary Ruben gazzar at email.com
Wed Nov 10 18:09:27 CST 2004

```Hi Nils,
How about transposing and subtracting it?

>>> a=array([[1,2,3],[2,1,4],[3,4,1]])
>>> a
array([[1, 2, 3],
[2, 1, 4],
[3, 4, 1]])
>>> b=transpose(a)
>>> b
array([[1, 2, 3],
[2, 1, 4],
[3, 4, 1]])
>>> a-b
array([[0, 0, 0],
[0, 0, 0],
[0, 0, 0]])

Alternatively, maybe you could sum along each axis of your matrix and compare the results?
eg.

>>> c=sum(a)
>>> d=sum(a,1)
>>> c
array([6, 7, 8])
>>> d
array([6, 7, 8])
>>> c-d
array([0, 0, 0])

I'm not sure whether there might be cases where this could falsely identify a matrix as symmetric - you'll have to have a think about this.
Gary R.

----- Original Message -----
>
> Hi all,
>
> Is it currently possible (by a built-in function)  to verify whether a
> matrix
> is symmetric or not.  I am  also interested in a
> built-in function for verifying the definiteness of a matrix ?
>
> Any suggestion or comment ?
>
> Nils

--
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