Basic Matlab Help...Please

I have 50 wave heights (H) and 50 corresponding wave frequencies (w) and I need to create 50 sine waves over a 30 minute period and then add them up.

I have tried:

S = H.*sin(w.*t) which does not work

and:

S_1 = H(1)*sin(w(1).*t)

which takes too long because I would have to do that 50 times and then later would have to do it 306 times.

I need a quicker way to do it that does element by element multiplication to create 50 sine waves and then add the sin waves up element by element.

Thank you

Answer 1

[Stephen]

I want to add each point of time together from the two sine waves...

i.e

Amplitude from wave 1 at time 1 sec + Amplitude from wave 2 at time 1 sec

but I need it for 30 mins and 50 waves.

Answer 2

[Tom]

I think that you have to have a for loop. What about

for t=1:1800
 S(t) = sum(H.*sin(w*t))
end

This should give you an array S that is the sum of all the waves at each second, so that (for example) S(61) will be the sum of the waves at 1 minute and 1 second and so on.... You should then be able to graph S as a function of time.

plot(S)

[Walter Roberson]

A for loop makes things easier and clearer, but see my new answer for a method without a for loop.

Answer 3

[Walter Roberson]

Let H, w, and t all be row vectors, and H and w must have the same number of elements but t can be different. Then you want

S = sum(bsxfun(@times,H(:),sin(bsxfun(@times,w(:),t))));

[Stephen]

I did it your way, but when I try plotting it I get nothing what so ever. Seems like the code should be correct, but idk

[Stephen]

I have noticed that this way only gives me a single answer instead of an array that allows me to create a SINE wave.

[Walter Roberson]

Hmmm, I did test before I posted. Are you sure your t is a *row* vector?

[Stephen]

Ignore my ignorance...I found my mistake it works great. Thank