How to minimize the loop function?

hello,,i need to simplify this coding,maybe by minimizing only one loop..i really don't know how to do it..please help me asap.

function S = IraHistFunction (im)

I = imread ('lena.jpg'); [m,n] = size (I); S = zeros (256, 1);

for GrayValue = 0 : 255

for i = 1 : m
  for j = 1 : n
    if I(i,j) == GrayValue
       S(GrayValue+1) = S(GrayValue+1) + 1 ;
    end
  end
end
end
figure, bar(S)

Answer 1

[Mohammad Abouali]

Change

for GrayValue = 0 : 255
  for i = 1 : m
    for j = 1 : n
      if I(i,j) == GrayValue
        S(GrayValue+1) = S(GrayValue+1) + 1 ;
      end
    end
  end
end

to a single line as follow:

n=hist(I(:),0:255);

You can then plot it as follow:

bar(0:255,n);

[siti]

ohh..thanks a lot..but can i minimize looping without using hist function?

[Mohammad Abouali]

If you insist on not using * hist * you can do it this way:

change this:

for GrayValue = 0 : 255
  for i = 1 : m
    for j = 1 : n
      if I(i,j) == GrayValue
        S(GrayValue+1) = S(GrayValue+1) + 1 ;
      end
    end
  end
end

to a code with only one loop as

for GrayValue = 0 : 255
  S(GrayValue+1)=sum(I(:)==GrayValue);
end

or even shorter without any loop as

S=arrayfun(@(x) (sum(I(:)==x)), 0:255);