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Re: Transposing a triangular matrix.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24368] Re: Transposing a triangular matrix.
  • From: d8442803 at student.nsysu.edu.tw (Wen-Feng Hsiao)
  • Date: Wed, 12 Jul 2000 23:13:10 -0400 (EDT)
  • Organization: NSYSU
  • References: <8k3o5s$41t@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Regarding transposing a triangular matrix (in list form), Rob Pratt has 
shown me a smart way by using Table to deal with an upper triangular 
input. According to his illustration I added the function for lower 
triangular input cases as below.

Wen-Feng
--------
upperTriTranspose[lis_List]:=Table[lis[[i,k+1-i]],{k,Length[lis]},{i,k}]
lowerTriTranspose[lis_List]:=
  Table[lis[[i,k]],{k,Length[lis]},{i,k, Length[lis]}]
triTranpose[lst_List]:=If[lowerTriMatrixQ[lst], 
      Return[lowerTriTranspose[lst]];,
      If[upperTriMatrixQ[lst],
        Return[upperTriTranspose[lst]];,
        Print["Not a triangular list!"]]];


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