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RE: matrix operations

• To: mathgroup at smc.vnet.net
• Subject: [mg46366] RE: [mg46329] matrix operations
• From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
• Date: Mon, 16 Feb 2004 23:41:52 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

>-----Original Message-----
>From: paolo tarpanelli [mailto:tarpanelli at libero.it]
To: mathgroup at smc.vnet.net
>Sent: Sunday, February 15, 2004 4:20 AM
>To: mathgroup at smc.vnet.net
>Subject: [mg46366] [mg46329] matrix operations
>
>
>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
>
>----------------
>

e.g.:

a = Array[x, {5, 4}];

Subtract @@@ Reverse /@ Partition[a, 2, 1] // TableForm

(#2 - #1 &) @@@ Partition[a, 2, 1] // TableForm


--
Hartmut Wolf