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 > > ----------------