How can I divide each row of a matrix by a fixed row?

Question

Suppose I have a matrix like:

100 200 300 400 500 600   1   2   3   4   5   6  10  20  30  40  50  60 ... 

I wish to divide each row by the second row (each element by the corresponding element), so I'll get:

100 100 100 100 100 100   1   1   1   1   1   1  10  10  10  10  10  10 ... 

Hw can I do it (without writing an explicit loop)?

Answer 1

Use bsxfun:

outMat = bsxfun (@rdivide, inMat, inMat(2,:)); 

The 1st argument to bsxfun is a handle to the function you want to apply, in this case right-division.

Answer 2

Here's a couple more equivalent ways:

M = [100 200 300 400 500 600      1   2   3   4   5   6      10  20  30  40  50  60];  %# BSXFUN MM = bsxfun(@rdivide, M, M(2,:));  %# REPMAT MM = M ./ repmat(M(2,:),size(M,1),1);  %# repetition by multiplication MM = M ./ ( ones(size(M,1),1)*M(2,:) );  %# FOR-loop MM = zeros(size(M)); for i=1:size(M,1)     MM(i,:) = M(i,:) ./ M(2,:); end 

The best solution is the one using BSXFUN (as posted by @Itamar Katz)