Re: matrix operations
- To: mathgroup at smc.vnet.net
- Subject: [mg46353] Re: matrix operations
- From: "Steve Luttrell" <steve1 at _removemefirst_luttrell.org.uk>
- Date: Mon, 16 Feb 2004 08:59:53 -0500 (EST)
- References: <c0mohe$65t$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Here is an example of what you want to do: a=Array[x,{10,3}] Map[(#1[[2]]-#1[[1]])&,Partition[a,2,1]] Steve Luttrell "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 > > ---------------- >