# Thread Subject: matrix multiplication problem

 Subject: matrix multiplication problem From: Milos Milenkovic Date: 7 Feb, 2012 18:26:10 Message: 1 of 4 A =      2 3 4 5 6 7      1 2 3 3 4 5 B =      0 2 4 2 3 4      3 4 6 4 7 8 >> A1 = A(:,1:3:n); A2 = A(:,2:3:n); A3 = A(:,3:3:n);  B1 = B(:,1:3:n); B2 = B(:,2:3:n); B3 = B(:,3:3:n);  C1 = A2*B1+(A1-A2)*B2; C2 = A2*B2; C3 = A3*B2+A2*(B3-B2);  C(:,3:3:end) = C3; C(:,2:3:end) = C2; C(:,1:3:end) = C1; Dear, what this means: ??? Error using ==> mtimes Inner matrix dimensions must agree. Best, Milos
 Subject: matrix multiplication problem From: Greg Heath Date: 7 Feb, 2012 19:29:03 Message: 2 of 4 On Feb 7, 1:26 pm, "Milos Milenkovic" wrote: > A = >      2     3     4     5     6     7 >      1     2     3     3     4     5 > > B = >      0     2     4     2     3     4 >      3     4     6     4     7     8 > > >> A1 = A(:,1:3:n); A2 = A(:,2:3:n); A3 = A(:,3:3:n); > >  B1 = B(:,1:3:n); B2 = B(:,2:3:n); B3 = B(:,3:3:n); >  C1 = A2*B1+(A1-A2)*B2; C2 = A2*B2; C3 = A3*B2+A2*(B3-B2); >  C(:,3:3:end) = C3; C(:,2:3:end) = C2; C(:,1:3:end) = C1; > > Dear, > what this means: > ??? Error using ==> mtimes > Inner matrix dimensions must agree. > Best, > Milos Delete the semicolons fom the end of the commands and inspect the result of each command. Hope this helps. Greg
 Subject: matrix multiplication problem From: Roger Stafford Date: 7 Feb, 2012 22:21:13 Message: 3 of 4 "Milos Milenkovic" wrote in message ... > A = > 2 3 4 5 6 7 > 1 2 3 3 4 5 > > B = > 0 2 4 2 3 4 > 3 4 6 4 7 8 > > >> A1 = A(:,1:3:n); A2 = A(:,2:3:n); A3 = A(:,3:3:n); > B1 = B(:,1:3:n); B2 = B(:,2:3:n); B3 = B(:,3:3:n); > C1 = A2*B1+(A1-A2)*B2; C2 = A2*B2; C3 = A3*B2+A2*(B3-B2); > C(:,3:3:end) = C3; C(:,2:3:end) = C2; C(:,1:3:end) = C1; > > Dear, > what this means: > ??? Error using ==> mtimes > Inner matrix dimensions must agree. > Best, > Milos - - - - - - - -   Milos, in that code I gave you in the other thread I intended to use 'end' instead of 'n'. They should read:  A1 = A(:,1:3:end); A2 = A(:,2:3:end); A3 = A(:,3:3:end);  B1 = B(:,1:3:end); B2 = B(:,2:3:end); B3 = B(:,3:3:end);  C1 = A2*B1+(A1-A2)*B2; C2 = A2*B2; C3 = A3*B2+A2*(B3-B2);  C(:,3:3:end) = C3; C(:,2:3:end) = C2; C(:,1:3:end) = C1; Using the original version, if you happened to have the wrong value for n floating around you would get the error you described. Roger Stafford
 Subject: matrix multiplication problem From: Milos Milenkovic Date: 8 Feb, 2012 06:26:10 Message: 4 of 4 "Roger Stafford" wrote in message ... > "Milos Milenkovic" wrote in message ... > > A = > > 2 3 4 5 6 7 > > 1 2 3 3 4 5 > > > > B = > > 0 2 4 2 3 4 > > 3 4 6 4 7 8 > > > > >> A1 = A(:,1:3:n); A2 = A(:,2:3:n); A3 = A(:,3:3:n); > > B1 = B(:,1:3:n); B2 = B(:,2:3:n); B3 = B(:,3:3:n); > > C1 = A2*B1+(A1-A2)*B2; C2 = A2*B2; C3 = A3*B2+A2*(B3-B2); > > C(:,3:3:end) = C3; C(:,2:3:end) = C2; C(:,1:3:end) = C1; > > > > Dear, > > what this means: > > ??? Error using ==> mtimes > > Inner matrix dimensions must agree. > > Best, > > Milos > - - - - - - - - > Milos, in that code I gave you in the other thread I intended to use 'end' instead of 'n'. They should read: > > A1 = A(:,1:3:end); A2 = A(:,2:3:end); A3 = A(:,3:3:end); > B1 = B(:,1:3:end); B2 = B(:,2:3:end); B3 = B(:,3:3:end); > C1 = A2*B1+(A1-A2)*B2; C2 = A2*B2; C3 = A3*B2+A2*(B3-B2); > C(:,3:3:end) = C3; C(:,2:3:end) = C2; C(:,1:3:end) = C1; > > Using the original version, if you happened to have the wrong value for n floating around you would get the error you described. > > Roger Stafford Dear Roger, thanks and once again thanks!! Sorry for this last stupid question, I didn't use Matlab for a long time. Some matrices are quadratic so n*3n is suitable, but for the other I will make appropriate adjustments that is not the problem. The computations for single case involve some 760*760, but for fuzzy that will be 760*(760*3). Sorry if I ask a few questions more. Best, Milos

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