MATLAB: How can I have all the for loop outputs in one matrix

foe loopquestion

for ii=1:3:numel(b) b(ii) end

Best Answer

ii=1:3 numel(b);
iwant=zeros(length(ii),1) ;
i=0;
for ii=1:3:numel(b)
 i=i+1;
 iwant(i)= b(ii);
end

Without loop:

iwant=b(1:3;numel(b));

Related Solutions

MATLAB: Access subarry from large file and loop through each subarry.

A_out = accumarray(A(:,1),(1:size(A,1))',[],@(x){A(x,:)});

other:

b = unique(A(:,1));
n = numel(b);
A_out = cell(n,1);
for ii = 1:n
    A_out{ii} = A(A(:,1) == b(ii),:);
end

MATLAB: What is another logic that has execution time faster than randi

I agree with Matt - I bet there are faster ways to run your loop, and we can probably help out if you can describe what the loop is meant to do...

Nevertheless one way to keep your current code structure but speed it up a bit would be to pre-compute a buffer of randi integers between 0 and 2, rather than calling randi multiple times in the loop like this:

A=8;
B=12;
C=10;
bufferSz = 5000;
randBuffer = randi([0 2], bufferSz, B);
randUpTo = 1;
RandomMatriceB = zeros(A,B,C);
for ii=1:C;    
    for x=1:2:A-1;
        %make first random matrice
        [vals RandomMatriceA(x,:,ii)]=sort(rand(1,B),2);   
        done=false;
        while ~done,
              %make row of second random matrice
              if randUpTo>bufferSz
                  randBuffer = randi([0 2], bufferSz, B);
                  randUpTo = 1;
              end
              NewRowRandomMatriceB = randBuffer(randUpTo,:);
              randUpTo = randUpTo + 1;
              %Make sure sum all element per row in RandomMatriceB <=11
              done=sum(NewRowRandomMatriceB)<12;
        end
        RandomMatriceB(x,:,ii)=NewRowRandomMatriceB;
        ...
    end
    for h=2:2:A;
        doneA=false;
        while ~doneA,
          [vals RandomMatriceA(h,:,ii)]=sort(rand(1,B),2);
          doneB=false;
          while ~doneB,
                 if randUpTo>bufferSz
                     randBuffer = randi([0 2], bufferSz, B);
                     randUpTo = 1;
                 end
                 NewRowRandomMatriceB = randBuffer(randUpTo,:);
                 randUpTo = randUpTo + 1;
                 doneB= sum(NewRowRandomMatriceB)<12;
          end
          RandomMatriceB(h,:,ii)=NewRowRandomMatriceB;
        ...
    end
    ...

If you know the absolute maximum number of randi() integers you'll need, you won't even need the "check" that I put in that makes sure you don't try to access integers beyond the buffer size.

Did this speed things up for you Febri?

Oh, and do you initialize RandomMatriceB to a particular size? It doesn't look so..., so I bet that you'll get even more speedup by putting this line at the start of your code:

RandomMatriceB = zeros(A,B,C);

In fact, now that I look at your code a bit more, I think this would be the main issue.

Best Answer

Related Solutions

MATLAB: Access subarry from large file and loop through each subarry.

MATLAB: What is another logic that has execution time faster than randi

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