MATLAB: Divide a matrix into small matrices with equal number of columns using “for” loop

for loopMATLABmatrix

I have a matrix with size 1*2809 . I want to loop the matrix and take 8 values at a time to perform element wise multiplication with another 8 bit size matrix. Either, what i want to do is divide the matrix, such that in the first iteration only the first 1:8 elements are taken, and, in second iteration, 8:16 elements are taken and so on.

How can I achieve this in matlab using "for" loop.

Best Answer

A for-loop is unnecessary. If A is the matrix you are trying to divide up into groups of 8 and B is the 8-vector you are multiplying them with, then do

C=reshape(A,8,[]).*B(:);
C=C(:).';

However, 92609 is not a multiple of 8, so fix that first.

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MATLAB: “for” loop question

Perhaps as follows? Basically, you've forgotten to index the element of QLBrainShift1a (and maybe also QLBrainShift1) that you're trying to operate on.

   point1=AmtOfPts1:-1:0;
   for i=1:length(point1)
    QLBrainShift1a(i) = QLBrainShift1(i)+error1-(point1(i)/AmtOfPts1)*error1;
   end

MATLAB: Writing a loop “for”

With a loop:

phi = zeros(1, 452);  % Instead of 450?
s   = 0;
m   = 1;
for k = 1:4:452
  phi(k:k+4) = (a_locs(k:k+4) - s) / a_odd(m);
  s = s + a_odd(m);
  m = m + 1;
end

And vectorized - assuming that a_odd is a row vector:

phi = reshape(a_locs, 4, 113);
phi = bsxfun(@minus, phi, [0, cumsum(a_odd(1:112)]);
phi = bsxfun(@rdivide, phi, a_odd(1:113));
phi = reshape(phi, 1, 452);

Best Answer

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