MATLAB: I need help with matrix size confliction in code

matrix error

function [xx,tt] = syn_sin(fk, Xk, fs, dur, tstart)
xx = 0;
M = length(fk);
Ts = 1/(fs);
s1 = fs*tstart;
s2 = fs*(dur + tstart);
n = s1:s2;
w = 2*pi*fk(1:M);
tt = (n*Ts);
x = real(Xk(1:M).*exp(j*w.*tt));
xx = xx + x;
plot(tt,xx);
So I'm getting this error: (ignore the line # I had comments in between the code)
Error using  .* 
Matrix dimensions must agree.
Error in syn_sin (line 58)
x = real(Xk(1:M).*exp(j*w.*tt));
Error in Untitled2 (line 8)
syn_sin([0,100,250],[10,14*exp(-j*pi/3),8*j],10000,0.1,0);
I'm basically trying to create a sin graph using the summation of A*E(jwt) but I can't get the vectorization method to work. I can use a for loop and it works but I'm trying to avoid using that. Any thoughts?
edit: fk, Xk, and w has 3 values and n and tt has 1001. The size confliction seems to not matter in a for loop but I can't get it to work when I vectorize it.

Best Answer

The error refers to the element-by-element multiplication "w.*tt". You are attempting to multiply the three elements of row vector 'w' by the thousand and one elements of 'tt', which doesn't make sense in matlab's syntax.
You mention "size confliction seems to not matter in a for loop", so my guess is that you wish to plot three different curves of 1001 points each, which is to say three different frequencies with 1001 time points each, but that is not what your attempt at vectorization accomplishes. You should state clearly what it is you are trying to do, so we wouldn't have to guess at it.
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