MATLAB: Vectorization – problem with zeros

vectorizationzeros

I need to expand a small matrix A into a bigger one according to a pattern defined by a an array R. But the array may contain zeros so as to know that the rows and columns marked''0'' should be omitted. Here are the matrices:
   A=[1 3 2 4;  R=[1;
      5 6 7 8;     3;
      9 1 2 3;     0;
      4 5 6 2];    7];
   R'=[1 3 0 7];
  % ... the resulting matrix would be:
  B=[1 0 3 0 0 0 4;
     0 0 0 0 0 0 0;
     5 0 6 0 0 0 8;
     0 0 0 0 0 0 0;
     0 0 0 0 0 0 0;
     0 0 0 0 0 0 0;
     4 0 5 0 0 0 2];
B=zeros(7,7); B(R,R')=A ……returns an error

Best Answer

  • Thank you Monkey, I really appreciate your help, but it seems that I've found a more effective solution:*
A=[1 3 2 4;  
   5 6 7 8;     
   9 1 2 3;     
   4 5 6 2]; 
R=[1 3 0 7];
B=zeros(7);
    RNZ=R(R ~= 0);   
    d=find(R);
    T=A(d,d');
    B(RNZ,RNZ')=T
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