Columnwise operation.

I was hoping someone could help me with quite a basic problem, i just think i've been looking at it too long to notice what i've been doing wrong.

I have P by T matrix, where P and T are the length of vectors containing different values of theta and phi. So every matrix element represents a position in theta and phi.

I want to multiply every element in a matrix by the sin of the angle of the column it is in. Eg, multiply all elements in the first column by sin(theta(1)) and elements in 2nd column by sin(theta(2)) and so on.

Here is what i have so far but it really isnt running correctly.

Can anyone help?

function Volume = Volume(theta, phi)

            R_Drop = 2e-6.*rand(45,45); 

            R_SQ = R_Drop.*R_Drop;

            R_SQ_s = zeros(size(R_SQ));

      for Th = 1:length(theta)

%%This is the line that is wrong, below. 

              R_SQ_s(:,Th) = (R_SQ(:,Th)).*sin(theta(Th));

      end

            Volume  = trapz(trapz((R_SQ_s)'));

Thanks a lot

Answer 1

[Andrei Bobrov]

R_SQ_s = ones(size(R_SQ),1)*sin(theta(:).').*R_SQ;

or

R_SQ_s = bsxfun(@times,R_SQ,sin(theta(:).'));