convolution in matlab

Hello!

I'm tryinig to write a simple convolution program in matlab, but i keep getting stuck!

Basically, I'm trying to convolve two signals:

1) x(t)=3sin(50*pi*t) + sin(220*pi*t) sample at 250Hz from 0 to .3 sec
2) g(t)=150*e^(-112t)*sin(112t) sampled at 250Hz from 0 to .1 sec

So, I know that the first signal will consist of 75 sample at 4ms intervals and the second will consist of 25 samples at 4ms intervals. I was able to graph the first fuction in matlab using the stem function.

I'm having a hard time graphing the second equation. I keep getting the following error:

??? Error using ==> *
Inner matrix dimensions must agree.

For equation 1 I defined t as such: 0:.004:.3 and for equation 2 I used a different variable, n, defined as 0:.004:.1.

Any help is greatly appreciated!

I think that instead of using the operator "*" you should use the operator ".*". ".*" is an "element-wise" multiplication instead of normal matrix multiplication which is performed by simply "*". For more information on the operator, type "help .*".

Added after 5 minutes:

Being more clear:

g(t)=150*e^(-112t)*sin(112t)

Click to expand...

This should be changed to

g(t)=150*e^(-112t).*sin(112t);

e^(-112t) and sin(112t) are both matrices, so you need to be careful on how they are getting multiplied.[/quote]

Thank you! That helped out a lot!!! Can I now just use CONV to do my convolution?

Can I now just use CONV to do my convolution?

Click to expand...

Yes, you should be able to just type...

y = conv(g, x);

The order of the arguments of conv() shouldn't matter.