MATLAB: How to reduce execution time of for loops in MATLAB

for loop

I am new to Matlab. I am doing project in communication. While doing convolutional encoding with for loop it takes around 200 sec to execute. How to reduce the execution time?Do any of you guys know how to make the code run faster?
for i=1:size(re_bin,1)/100
    coded_data1(i,:)=convenc(re_bin(i,:),trellis);
end
encodedData= coded_data1;
for j=1:100
    for k=(j*size(re_bin,1)/100)+1: (j+1)*size(re_bin,1)/100  
        coded_data(k-(j*size(re_bin,1)/100),:)=convenc(re_bin(j*size(re_bin,1)/100,:),trellis);
    end
    encodedData1(:,:,j)= coded_data;
end
codedata=encodedData1;
finalCodeddata=cat(3,encodedData,codedata);

Best Answer

s100 = size(re_bin,1) / 100;
% Pre-allocate:
encodedData = zeros(s100, 0);  % Better define 2nd dimension correctly
for i = 1:s100
  encodedData(i, :) = convenc(re_bin(i,:), trellis);
end
encodedData1 = zeros(100, ???, 100);  % Sorry, no idea what to insert for ???
for j = 1:100
  tmp = convenc(re_bin(j * s100, :), trellis);
  for k = (j*s100)+1:(j+1)*s100  
    encodedData1(k - j * s100, :, j) = tmp;
  end
end
finalCodeddata = cat(3,encodedData, encodedData1);
The pre-allocation is essential for speed. It looks like "encodedData1" is very redundant. You should replace the loop over k by a repmat command:
for j = 1:100
  tmp = convenc(re_bin(j * s100, :), trellis);
  encodedData1(:, :, j) = repmat(tmp, 100, 1);
end
Do I see correctly, that the indices in "encodedData1(k - j * s100, :, j)" are 1:100 in each iteration? Sorry, I cannot test this by running your code, because I do not have the required toolbox.
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