Re: matrix operations
- To: mathgroup at smc.vnet.net
- Subject: [mg46350] Re: [mg46329] matrix operations
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Mon, 16 Feb 2004 08:59:51 -0500 (EST)
- References: <200402150319.WAA06236@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
On 15 Feb 2004, at 04:19, 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 > > One out of many ways: mat = Array[a, {3, 3}] {{a[1, 1], a[1, 2], a[1, 3]}, {a[2, 1], a[2, 2], a[2, 3]}, {a[3, 1], a[3, 2], a[3, 3]}} Transpose[(Drop[RotateLeft[#] - #, -1] & ) /@ Transpose[mat]] {{a[2, 1] - a[1, 1], a[2, 2] - a[1, 2], a[2, 3] - a[1, 3]}, {a[3, 1] - a[2, 1], a[3, 2] - a[2, 2], a[3, 3] - a[2, 3]}} Andrzej Kozlowski Chiba, Japan http://www.mimuw.edu.pl/~akoz/
- References:
- matrix operations
- From: "paolo tarpanelli" <tarpanelli@libero.it>
- matrix operations