Re: Element extraction
- To: mathgroup at smc.vnet.net
- Subject: [mg19604] Re: Element extraction
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sat, 4 Sep 1999 21:09:13 -0400
- References: <7qqau1$4c5@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Mark Lawrence Storch <mscc+ at andrew.cmu.edu> wrote in message news:7qqau1$4c5 at smc.vnet.net... > Hello, > I am having a bit of trouble trying to extract elements out of > nested lists. I have an X x Y array where each element of the array is > a 3x3 matrix. I am trying to make density plots of each component. For > example, I would like to plot the 1,1 components of each element of the > larger array. I have tried the following: > > Array[g[[i,j][[a,b]],{i,Dimensions[g][[1]]},{j,Dimensions[g][[2]]}] > > where I am trying to get the a,b component > > This does not work, and I am not seeing exactly why not. I am hoping > someone can point out my error or suggest a way to extract the lists I > need. > > Thank you, > Mark Storch > Carnegie Mellon University > Department of Materials Science > Mark, One way: data = Array[a, {2, 2, 2, 2}] {{{{a[1, 1, 1, 1], a[1, 1, 1, 2]}, {a[1, 1, 2, 1], a[1, 1, 2, 2]}}, {{a[1, 2, 1, 1], a[1, 2, 1, 2]}, {a[1, 2, 2, 1], a[1, 2, 2, 2]}}}, {{{a[2, 1, 1, 1], a[2, 1, 1, 2]}, {a[2, 1, 2, 1], a[2, 1, 2, 2]}}, {{a[2, 2, 1, 1], a[2, 2, 1, 2]}, {a[2, 2, 2, 1], a[2, 2, 2, 2]}}}} Map[#[[1, 1]] &, data, {2}] {{a[1, 1, 1, 1], a[1, 2, 1, 1]}, {a[2, 1, 1, 1], a[2, 2, 1, 1]}} Map[#[[2, 1]] &, data, {2}] {{a[1, 1, 2, 1], a[1, 2, 2, 1]}, {a[2, 1, 2, 1], a[2, 2, 2, 1]}} Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565