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Re: Transpose[A]*A wrong?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg41165] Re: [mg41129] Transpose[A]*A wrong?
  • From: Selwyn Hollis <selwynh at earthlink.net>
  • Date: Tue, 6 May 2003 06:00:47 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Matrix multiplication is done with Dot. What you want is

   Transpose[A].A

-----
Selwyn Hollis
http://www.math.armstrong.edu/faculty/hollis

On Monday, May 5, 2003, at 02:40  AM, Daniel Lidström 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.
> Thanks!
>
> /Daniel
>
> -- 
>
> Daniel Lidström
>
> 62 23' 25" N
> 17 15' 31" E
>
>
>
>




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