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can this loop be vectorized ?

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Miguel Reina
Miguel Reina 2017-11-27
评论： Guillaume 2017-11-27
I am trying to make a function for an histogram to explain the concept to students, is possible to vectorize this loop?
[x,y]=size(A);
freq=zeros(256,1);
for i=1:x
for j=1:y
value=A(i,j);
freq(value+1)=freq(value+1)+1;
end
end
thanks in advance.

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采纳的回答

Guillaume
Guillaume 2017-11-27
Very simply with:
freq = accumarray(A(:), 1, [256, 1]);
  2 个评论
Miguel Reina
Miguel Reina 2017-11-27
This error is appearing "Error using accumarray First input SUBS must contain positive integer subscripts." the Matrix A contains uint8 values and the size is 594x671
Guillaume
Guillaume 2017-11-27
Yes, somehow I missed the +1 in your code. The correct answer should be:
freq = accumarray(A(:) + 1, 1, [256, 1]);

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