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MathGroup Archive 2004

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Re: matrix operations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46385] Re: matrix operations
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Mon, 16 Feb 2004 23:42:19 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <c0mohe$65t$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

a = Table[x[j, i], {i, 3}, {j, 3}];

Drop[RotateLeft[a] - a, -1]

Regards
  Jens

paolo tarpanelli wrote:
> 
> If I have a matrix
> 
> a={x[[1,1]],x[[1,2]],...,x[[1,n]]}
>     {x[[2,1]],x[[2,2]],...,x[[2,n]]}
>             .
>             .
>             .
>     {x[[m,1]],x[[m,2]],...,x[[m,n]]}
> 
> how can I compute the difference between any element and the previous for each column :
> 
> aa={x[[2,1]]-x[[1,1]], x[[2,2]]-x[[1,2]],...,x[[2,n]]-x[[1,n]]}
>       {x[[3,1]]-x[[2,1]], x[[3,2]]-x[[2,2]],...,x[[3,n]]-x[[2,n]]}
>             .
>             .
>             .
>       {x[[m,1]]-x[[m-1,1]],x[[m,2]]-x[[m-1,2]],...,x[[m,n]]-x[[m-1,n]]}
> 
> ------------------------------------------------------------------------------------------------------
> 
> I built this code but it does not work
> 
> r=Array[0,{m,n}]
> For[j=1,j=n,j++
>        r[[i,j]]=Table[a[[i+1,j]]-a[[i,j]],{i,1,m-1,1}]]
> 
> thanks
> 
> Paolo
> 
> ----------------


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