Re: Transpose[A]*A wrong?
- To: mathgroup at smc.vnet.net
- Subject: [mg41168] Re: Transpose[A]*A wrong?
- From: Paul Abbott <paul at physics.uwa.edu.au>
- Date: Tue, 6 May 2003 06:01:22 -0400 (EDT)
- Organization: The University of Western Australia
- References: <b950vl$r49$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
In article <b950vl$r49$1 at smc.vnet.net>,
"Daniel Lidström" <daniel.lidstrom at _DELETE_home.se> wrote:
> Hi,
>
> why does Mathematica give the wrong result here?
>
> In[1]:= \!\(A\ = \ {{x\_11, x\_12, x\_13}, {x\_21, x\_22, x\_23}, {x\_31,
> x\_32,
> x\_33}}\)
>
> Out[1]= {{x , x , x }, {x , x , x }, {x , x , x }}
> 11 12 13 21 22 23 31 32 33
>
> In[2]:= Transpose[A]*A
>
> 2 2
> 2
> Out[2]= {{x , x x , x x }, {x x , x , x x }, {x x , x x
> , x }}
> 11 12 21 13 31 12 21 22 23 32 13 31 23
> 32 33
>
> Look at the diagonal elements for example.
You want
Transpose[A] . A
not * which gives element-by-element multiplication.
Cheers,
Paul
--
Paul Abbott Phone: +61 8 9380 2734
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