How to remove the for loop in this code?

Question

Shreyas Kamath 2016-5-26

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https://ww2.mathworks.cn/matlabcentral/answers/285889-how-to-remove-the-for-loop-in-this-code

评论： Shreyas Kamath 2016-6-15

Hi, I am working on a code related to matching score calculation which is provided below:

    ref_points=size(tpol,1); %number of rows=number of referenence image points
    in_points=size(ipol,1); %number of rows=number of input image points
   radsize=7*ones(ref_points,1);
   angsize=11* ones(ref_points,1);
   radlow=-radsize./2;radhigh=radsize./2;anglow=-angsize./2;anghigh=angsize./2;
   epsillon=10;
   mscore=0;
   for i=1:ref_points
      for j=1:in_points
        rdiff=tpol(i,1)-ipol(j,1);
        ediff=tpol(i,2)-ipol(j,2);
        thetadiff=tpol(i,3)-ipol(j,3);
        if ((radlow(i) < rdiff) && (rdiff < radhigh(i)) && (anglow(i) < ediff) && ...
            (ediff < anghigh(i)) && (abs(thetadiff) < epsillon) && ...
            (tpol(i,4)==ipol(j,4)))
            mscore=mscore+1;
            tpol(i,4)=3; %Change type 
        end
      end
    end
  end

I am interested to reduce the for loop as it takes high computation time. It would be very helpful if anyone could guide me through this. Thanks in advance.

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Answer 1

Andrei Bobrov 2016-5-26

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https://ww2.mathworks.cn/matlabcentral/answers/285889-how-to-remove-the-for-loop-in-this-code#answer_223482

编辑：Andrei Bobrov 2016-5-26

在 MATLAB Online 中打开

r = [-3.5 3.5];
a = [-5.5 5.5];
ep = 10;
ti = bsxfun(@minus,tpol,permute(ipol,[3 2 1]));
p = all([bsxfun(@gt,ti(:,1:2,:),[r(1),a(1)]) & bsxfun(@lt,ti(:,1:2,:),[r(2),a(2)]),...
 ti(:,3,:) < ep, ti(:,4,:) == 0],2);
mscore = nnz(p);
tpol(any(p,3),4) = 4;

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Shreyas Kamath 2016-5-26

The first mat file has equal number of ipol and tpol data (same values)as both are same image to be matched. Whereas the second mat file has different data i.e. two different images are being matched.

Shreyas Kamath 2016-6-15

I was trying to figure out the problem, it seems that

(tpol(i,4)==ipol(j,4)))

provides a different value when compared to

ti(:,4,:) == 0

The logic is correct. But the answer do not match. The rest of the "if conditions" work and provide the same answer. It would be helpful if you could help me solve this.

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How to remove the for loop in this code?

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How to remove the for loop in this code?

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