Re: Given a matrix, find position of first non-zero element in each

*To*: mathgroup at smc.vnet.net*Subject*: [mg99510] Re: Given a matrix, find position of first non-zero element in each*From*: Albert Retey <awnl at gmx-topmail.de>*Date*: Thu, 7 May 2009 06:32:44 -0400 (EDT)*References*: <gtrl9k$242$1@smc.vnet.net>

Hi, > This is how I solved this problem and after a bit of struggle. I wanted to > see if I could avoid using a Table, and solve it just using Patterns and > Position and Select, but could not so far. > > > Table[Flatten[{i, Flatten[Position[A[[i,All]], _?(#1 != 0 & ), 1, 1]]}], {i, > 1, 6}] > > Out[174]= {{1, 3}, {2, 1}, {3, 2}, {4, 1}, {5, 2}, {6, 2}} > > I am not happy with the above solution. I am sure there is a better one (the > above also do not work well when one row has all zeros). > > Do you see a better and more elegant way to do this? I absolutley don't think that it is a value per se to avoid Table, but here is one solution without Table: MapIndexed[Flatten[{#2, Position[#1, _?(# != 0 &), 1, 1]}] &,A] hth, albert