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MathGroup Archive 2004

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infinity expression from matrix inverse

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49800] infinity expression from matrix inverse
  • From: "Xiao Huang" <xiaohda at hotmail.com>
  • Date: Sun, 1 Aug 2004 04:10:03 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Friends,

Recently I've been having this problem with Mathematica 5.0: In the follwing 
program, when I set t=2 to 11, mathematica can give me the inverse of matrix 
n0, but for t >=12, it fails to produce the inverse due to infinity 
expressions. Can anyone explain this to me? (I guess the problem occurs in 
the last line.) Thanks a lot!  Those a1,a2,n0,n0s,nn,c you see in the 
following program are just some matrices.

Best Regards,

Xiao

\!\(<< LinearAlgebra`MatrixManipulation`\[IndentingNewLine]
  \(Remove["\<Global`*\>"];\)\[IndentingNewLine]
  \(ó = 8;\)\[IndentingNewLine]
  \(t = 11;\)\[IndentingNewLine]
  \(â = 0.6;\)\[IndentingNewLine]
  \(a1 = AppendRows[\ \ \ \ IdentityMatrix[\ t - 1\ ]\ , \ \ \ Table[\ 0\ , 
\ \
{\ t - 1\ }, \ {\ 1\ }\ ]\ \ \ \ ];\)\[IndentingNewLine]
  \(a2 = AppendRows[\ \ \ \ Table[\ 0\ , \ {\ t - 1\ }, \ {\ 1\ }\ ]\ , \ \ 
\
IdentityMatrix[\ t - 1\ ]\ \ \ \ \ ];\)\[IndentingNewLine]
  \(nn = Transpose[a1] . a1;\)\[IndentingNewLine]
  \(n1 = Transpose[a1] . a2;\)\[IndentingNewLine]
  \(c = IdentityMatrix[t] + AppendColumns[\ Table[0, \ {1}, \ {t}],
    AppendRows[\ \ \(-â\)*IdentityMatrix[t - 1], \
  Table[\ 0, \ {t - 1}, \ {1}\ ]\ ]\ ];\)\[IndentingNewLine]
  \(vc = ó\^2*Inverse[c] . Transpose[Inverse[c]];\)\[IndentingNewLine]
  \(n0 = IdentityMatrix[t]\  + \ 2  x*vc . nn;\)\[IndentingNewLine]
  \(Print[\ MatrixForm[n0]\ ];\)\[IndentingNewLine]
  \(n2 = Inverse[n0] . vc;\)\[IndentingNewLine]
  \)

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