Set up an example problem:
x=rand(1,1000);
y=rand(1,1000);
z=rand(1,1000);
t = [1:1000]/1000;
% calculate your function
f = x.*y./z;
plot(t,f)
Note that .* and ./ are elementwise multiplication and division, performing your function on each element separately and returning an array of the same size.
(note: if you have vectors x,y,z, then you can't index by fractions. But, it doesn't sound like you actually need to)
