Vectorizing three nested loops

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AP
AP 2012-10-13
Dear All,
How can I vectorize the following three nested loops? I tried using arrayfun but I did not succeed in doing it.
% Range of random number for x and y.
L = 8;
H = 6;
% The number of random numbers.
n = 100;
% Randomly spaced data.
x = rand( n, 1 )*L;
y = rand( n, 1 )*H;
d = .01;
[ X, Y ] = meshgrid( 0:d:L, 0:d:H );
TOL = .01;
I = zeros(size(X));
for i=1:size(X,1)
for j=1:size(X,2)
for k=1:numel(x)
dist = (X(i,j)-x(k))^2+(Y(i,j)-y(k))^2;
if( dist<TOL)
I(i,j) = 1;
end
end
end
end
Thanks,
Ahmad

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采纳的回答

Matt Fig
Matt Fig 2012-10-13
编辑：Matt Fig 2012-10-13
I2 = any((bsxfun(@minus,X,reshape(x,1,1,n)).^2 +...
bsxfun(@minus,Y,reshape(y,1,1,n)).^2)<TOL,3) ;
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Matt Fig
Matt Fig 2012-10-13
编辑：Matt Fig 2012-10-13
The code above does give the same result here.....
isequal(I,I2)
ans =
1
I ran it 10 times, and every time I get the same thing. Here is the code I used to test that I and I2 are equal. So what are you doing that says they are not equal? Did you run something other than what you posted?
% Range of random number for x and y.
L = 8;
H = 6;
% The number of random numbers.
n = 100;
% Randomly spaced data.
x = rand( n, 1 )*L;
y = rand( n, 1 )*H;
d = .01;
[ X, Y ] = meshgrid( 0:d:L, 0:d:H );
TOL = .01;
tic
I = zeros(size(X));
for i=1:size(X,1)
for j=1:size(X,2)
for k=1:numel(x)
dist = (X(i,j)-x(k))^2+(Y(i,j)-y(k))^2;
if( dist<TOL)
I(i,j) = 1;
end
end
end
end
toc
tic
I2 = any((bsxfun(@minus,X,reshape(x,1,1,n)).^2 +...
bsxfun(@minus,Y,reshape(y,1,1,n)).^2)<TOL,3) ;
toc
isequal(I,I2)
AP
AP 2012-10-13
Sorry, I did not noticed one of the statements had been changed. I get the same results too. Thanks so much.

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