MATLAB: Expand 1-D array to 2-D matrix using ‘ones’ function and colon ‘:’

matrix manipulation

Example:
matrixA = 6:10;
matrixA = matrixA(ones(1,5), :);
or:
matrixB = (6:10)';
matrixB = matrixB(:, ones(1,5));
My Question:
What's going on here? I just don't get it. Is there any reference on this "exotic" usage? Many thanks for any inputs!

Best Answer

It is not that crazy. It is basically
matrixA = 6:10;
for ii = 1:5
  for jj = 1:5
    temp(ii, jj) = matrixA(1, jj);
  end
end
matrixA = temp;
but lump together into a vectorized version. You can get rid of the inner loop with:
matrixA = 6:10;
for ii = 1:5
  temp(ii, :) = matrixA(1, :);
end
matrixA = temp;
and you can finally get rid of all loops with
matrixA = 6:10;
temp = matrixA(ones(1,5), :);
matrixA = temp;
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