Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2004
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2004

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: matrix operations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46345] Re: matrix operations
  • From: drbob at bigfoot.com (Bobby R. Treat)
  • Date: Mon, 16 Feb 2004 08:59:47 -0500 (EST)
  • References: <c0mohe$65t$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

m = 4; n = 3;
a = Array[x, {m, n}]
Most[RotateLeft@a - a]
Drop[RotateLeft@a - a, -1]

Most is new in version 5, but Drop is venerable.

Bobby

"paolo tarpanelli" <tarpanelli at libero.it> wrote in message news:<c0mohe$65t$1 at smc.vnet.net>...
> 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
> 
> ----------------


  • Prev by Date: Solve or LinearSolve or ...?
  • Next by Date: Re: how to explain this weird effect? Integrate
  • Previous by thread: Re: matrix operations
  • Next by thread: RE: matrix operations