Very helpful! At least I can use +/ .* for an iterative solution to Lp=I, solving for p. But why can’t I always get an inverse? (Even with non -infinite resistances, I get domain errors.)
a=.L 2 2;3 1;1 4 a 4 _2 0 0 0 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 8 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 8 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 8 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 1004 0 0 0 _2 _1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 0 8 _2 0 0 0 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 12 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 1010 _2 0 0 _2 _1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 2008 _1000 0 0 _1000 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _1000 0 0 0 _1000 4000 0 0 0 _1000 _1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 0 8 _2 0 0 0 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 1009 _1000 0 0 _2 _1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _1000 _1000 0 0 _1000 5999 _1000 0 0 _999 _1000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _1000 0 0 _1000 2008 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _1000 0 0 0 _2 1006 0 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 0 7 _1 0 0 0 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _1 _999 0 0 _1 1004 _1 0 0 _1 _1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _1000 _2 0 0 _1 1009 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 12 _2 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 0 0 0 _2 8 0 0 0 _2 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _1 0 0 0 5 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _1 _2 0 0 _2 7 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 8 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 _2 0 0 _2 8 _2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 _2 0 0 0 _2 4 -/ . * a _8.08478e26 %. a |domain error | %.a Brian Babiak MD https://drbabiak.com 167 Ridgecrest Rd. Ithaca NY 14850 – 9449 (607) 379 – 1335 fax (866) 813 – 4158 Payment links: http://PayPal.Me/BrianBabiakMD http://mkt.com/brian-babiak-md On 7/28/17, 1:03 AM, "Programming on behalf of 'Jon Hough' via Programming" <programming-boun...@forums.jsoftware.com on behalf of programm...@jsoftware.com> wrote: Matrix product is +/ .* (dyadic) determinant is -/ .* (monadic) see: http://code.jsoftware.com/wiki/Vocabulary/dot The matrix g is singular (since the rows are identical) and has no inverse. Hence %. gives an error. i.e. (-/ .*) g is zero. Hope that helps. Jon -------------------------------------------- On Fri, 7/28/17, Brian Babiak <bdbab...@gmail.com> wrote: Subject: [Jprogramming] Matrix operations questions To: programm...@jsoftware.com Date: Friday, July 28, 2017, 1:56 PM I’m working on a project to compute the distance resistance between two vertices in an electronic grid. I will share that later. But I am having domain error issues with matrix inverse and matrix product operations. See the following: f=.2 2$3 4 1 4 g=.2 2$i.2 h=.2 2$_3 4 2 _3 2 3$'f';'g';'h';f;g;h ┌───┬───┬─────┐ │f │g │h │ ├───┼───┼─────┤ │3 4│0 1│_3 4│ │1 4│0 1│ 2 _3│ └───┴───┴─────� 2 3$'$f';'$g';'$h';($f);($g);($h) ┌───┬───┬───┐ │$f │$g │$h │ ├───┼───┼───┤ │2 2│2 2│2 2│ └───┴───┴───� f . g |domain error | f .g f . h |domain error | f .h %. f 0.5 _0.5 _0.125 0.375 %. g |domain error | %.g f . f |domain error | f .f g . g |domain error | g .g h . h |domain error | h .h h * g 0 4 0 _3 The answers to all these operations are simple. Why are there these domain errors? Here is the project this issue is coming up in, although I believe it is more basic than that. vw=: (,@(((_ 0)$~#@:])`]`(1$~,~@:}.@[)}))`(,@(((0 _)$~#@:])`]`(1$~,~@:}.@[)}))@.(<:@:({.@:[)) NB. (moveno boardsz) nw (x1 y1;x2 y2; etc) NB. Gives vertex weights for a move list of a game as vector rows=: <"1 cols=: <"1@|: diags=: (-.((0;_1)&{))@:(</.) a=: 3 3$i.9 conndiag=: 3 : 0 r=. r,.|.r [ r=. >0{z [ i=. 1 [ n=. #z [ z=. diags y while. i<n do. col=. >i{z i=. >:i adds=. >2<\col r=. r,adds r=. r,(|."1 adds) end. ) connsq=: 3 : 0 r=. 0 2$0 [ i=. 0 [ n=. #z [ z=. y while. i<n do. col=. >i{z i=. >:i adds=. >2<\col r=. r,adds r=. r,(|."1 adds) end. ) connrws=: connsq@:rows conncls=: connsq@:cols edges=: 3 : 0 NB. takes board size as argument a=. (2$bs)$i.*:bs [ bs=. y r=. (connrws a),(conncls a) r=. r,conndiag a ) BOARDSZ=: 5 EDGES=: edges BOARDSZ VPLYR=: 1 NB. whether the vertical player is first or second A=: 3 : 0 mat=. (2$netsz)$0 [ netsz=. *:BOARDSZ [ j=. 0 [ i=. 0 [ arg=. VPLYR,BOARDSZ if. y=0 do. pcweights=. netsz$1 else. pcweights=. arg vw y end. while. i<netsz do. while. j<netsz do. mat=. (0{(((1 2$i,j) e. EDGES)*((i{pcweights)+j{pcweights))) (<(i,j))}mat j=. >:j end. j=. 0 i=. >:i end. mat ) D=: 3 : 0 diag=. (2$netsz)$ 1,netsz#0 [ netsz=. *:BOARDSZ [ colsum=. +/y [ y=. A y r=. colsum*diag ) L=: D-A NB. the Laplacian NB. %. Laplacian or . (dot) for Laplacian times current gives domain errors Any help would be appreciated! Brian Babiak MD https://drbabiak.com ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
