New uses for Matrix Multiplication

I wish I'd known MATLAB had...     matrix multiplication

• Often overlooked, matrix multiplication can do many useful things!
• Using multiplication instead of repmat. If you have a column vector V, and you want to repeat it horizontally 5 times,

• REPMAT(V, 1, 5)  is the same as
          V*[1 1 1 1 1].
• REPMAT(V,1,10) is the same as
         V*ones(1,10)
• REPMAT(V, 1, length(V)) will make a square, and so will V*(1+0*V)
• You can create the times table for 1 to 12 with [1:12]'*[1:12]
• Using multiplication instead of SUM. If you have a column vector V, and you want to sum it,
• SUM(V)  is the same as (1+0*V)'*V     note that 0*V is a handy way of creating a zero matrix of the same size as V.
• if you want a weighted sum, where W is the weights, 
  SUM(V.*W) is the same as V'*W   or W'*V.