assembling a correlation matrix

Hi,

I am creating a correlation matrix (H) using the following routine. However for large values of M,N it takes a long time to create H. I was wondering if there other ways of creating H more efficiently.

X=15;
%
N=10;M=20;
K=randi(X,M,N);
L=randi(X,M,N);
H=zeros(X,X);
for k=1:X
  for l=1:X
      H(k,l)=hsum(k,l,K,L,M,N);
  end
end

%where hsum is the following function

function ret=hsum(x,y,C,G,M,N)

ret=0;
for i=1:M
  for j=1:N
      if(C(i,j)==x && G(i,j)==y)
          ret= ret+1;
      end
  end
end

Thanks Mark

Answer 1

[Azzi Abdelmalek]

You can change your function

function ret=hsum(x,y,C,G,M,N)
a=C(1:M,1:N);
b=G(1:M,1:N);
ret=sum(find(C==x and G==y));

[Azzi Abdelmalek]

Bush Merc commented

Thanks for the suggestion. Unfortunately it is slower than the "for" loop.

function ret=hsum(x,y,C,G,M,N)
ret=sum(logical(find(C==x & G==y)));

[Azzi Abdelmalek]

try

unction ret=hsum(x,y,C,G,M,N)
ret=sum(C==x & G==y);

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