How to minimize the loop function?

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siti
siti 2014-10-31
编辑： Mohammad Abouali 2014-10-31
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)

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Mohammad Abouali
Mohammad Abouali 2014-10-31
编辑：Mohammad Abouali 2014-10-31
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);
  2 个评论
siti
siti 2014-10-31
ohh..thanks a lot..but can i minimize looping without using hist function?
Mohammad Abouali
Mohammad Abouali 2014-10-31
编辑：Mohammad Abouali 2014-10-31
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);

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