Re: Matrix Inverse Issue
- To: mathgroup at smc.vnet.net
- Subject: [mg80634] Re: Matrix Inverse Issue
- From: "Brian Gladman" <brg at nowhere.org>
- Date: Sun, 26 Aug 2007 23:28:42 -0400 (EDT)
- References: <far922$3t8$1@smc.vnet.net>
"Brian Gladman" <brg at nowhere.org> wrote in message news:far922$3t8$1 at smc.vnet.net... >I am having a problem with the matrix inverse for the following matrix in > Mathematica 6: > > A = Table[If[j == i, 1 - i/10, If[j == i + 1, i/10, 0]], {i, 9}, {j, 9}] > > {{9/10, 1/10, 0, 0, 0, 0, 0, 0, 0}, {0, 4/5, 1/5, 0, 0, 0, 0, 0, > 0}, {0, 0, 7/10, 3/10, 0, 0, 0, 0, 0}, {0, 0, 0, 3/5, 2/5, 0, 0, 0, > 0}, {0, 0, 0, 0, 1/2, 1/2, 0, 0, 0}, {0, 0, 0, 0, 0, 2/5, 3/5, 0, > 0}, {0, 0, 0, 0, 0, 0, 3/10, 7/10, 0}, {0, 0, 0, 0, 0, 0, 0, 1/5, 4/ > 5}, {0, 0, 0, 0, 0, 0, 0, 0, 1/10}} > > A Inverse[A] > > {{1, -1/72, 0, 0, 0, 0, 0, 0, 0}, {0, 1, -1/14, 0, 0, 0, 0, 0, 0}, {0, > 0, 1, -3/14, 0, 0, 0, 0, 0}, {0, 0, 0, 1, -8/15, 0, 0, 0, 0}, {0, > 0, 0, 0, 1, -5/4, 0, 0, 0}, {0, 0, 0, 0, 0, 1, -3, 0, 0}, {0, 0, 0, > 0, 0, 0, 1, -49/6, 0}, {0, 0, 0, 0, 0, 0, 0, 1, -32}, {0, 0, 0, 0, > 0, 0, 0, 0, 1}} > > I expected the identity matrix here but I get extra terms. > > Am I doing something wrong? > > Brian Gladman Ok, I now know I need a '.' for matrix multiplication. Brian Gladman