Re: Partition a list based on columns

*To*: mathgroup at smc.vnet.net*Subject*: [mg119683] Re: Partition a list based on columns*From*: Ray Koopman <koopman at sfu.ca>*Date*: Fri, 17 Jun 2011 00:09:45 -0400 (EDT)*References*: <itcdai$d13$1@smc.vnet.net>

On Jun 16, 1:02 am, StatsMath <stats.ma... at gmail.com> wrote: > [...] > > What would be a good way to line up elements in a list in a diagonal > fashion, for ex: from Range[9] want to create the follwing matrix: > > 1 2 4 > 3 5 7 > 6 8 9 > > Thanks in advance! This will give an r x c matrix whose elements are the integers 1...r*c in the positions you asked for: m[r_,c_] := With[{d = Which[ r < c-1, Join[Range[ r ],Table[r,{c-2-r}],Range[ r ,1,-1]], r > c-1, Join[Range[c-1],Table[c-1,{r-c}],Range[c-1,1,-1]], True , Join[Range[c-2], Range[c-1,1,-1]]]}, Partition[FoldList[Plus,0,d],c,1] + Range@r] m[3,5] //TableForm 1 2 4 7 10 3 5 8 11 13 6 9 12 14 15