Re: Matrix Element Extraction

*To*: mathgroup at smc.vnet.net*Subject*: [mg46640] Re: [mg46622] Matrix Element Extraction*From*: Tomas Garza <tgarza01 at prodigy.net.mx>*Date*: Thu, 26 Feb 2004 17:53:30 -0500 (EST)*References*: <200402251807.NAA05947@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Well, I must admit you produced an admirably complicated code! Still, it doesn't give what you want. Try this: In[1]:= mat = {{1, 2, 1}, {4, 5, 6}, {7, 8, -Infinity}}; size = Dimensions[mat]; Cases[Position[mat, x_ /; IntegerQ[x]], y_ /; Length[y] == 2 && First[y] == First[size] || Last[y] == Last[size]] Out[3]= {{1, 3}, {2, 3}, {3, 1}, {3, 2}} Tomas Garza Mexico City ----- Original Message ----- From: "Curt Fischer" <crf3 at po.cwru.edu> To: mathgroup at smc.vnet.net Subject: [mg46640] [mg46622] Matrix Element Extraction > In a matrix, I want to find the positions of all the integer elements in the > rightmost column or the bottom row. > > In[1]:= > mat={{1,2,1},{4,5,6},{7,8,-Infinity}} > > Out[1]= > {{1,2,1},{4,5,6},{7,8,-Infinity}} > > In[2]:= > Position[Map[((MemberQ[Union[Flatten[{mat[[Length[mat]]], > mat[[All,Dimensions[mat][[ > 2]] ]]}]],#])&&(#!=-Infinity))&,mat,{2}],True] > > Out[2]= > {{1,1},{1,3},{2,3},{3,1},{3,2}} > > This _mostly_ does what I want, but took me forever to think of. I'm > convinced there must be an easier way... > > Especially, is there an easy way to keep the point {1,1} from appearing on > this > list, other than using a replacement rule and an If[] command? ({1,1} is > not a position in the bottom row or right most column, so I don't want this > point returned.) > > Thanks for any advice. > > -- > Curt Fischer > > >

**References**:**Matrix Element Extraction***From:*"Curt Fischer" <crf3@po.cwru.edu>