Simple MATLAB (noob) question

Hello,

I not a frequent user to this program and I'm running into a little problem regarding graphing a function.

First I input this: x = 0:pi/15:4*pi

so that I can develop a range of the x values next I enter: y = (2*cos(60*x))

but it all comes out equaling two, when it shouldn't. I don't know where I'm going wrong. Help would be appreciated.

Answer 1

[Wayne King]

The way you set your x vector and then multiply by 60, you have increments of 4*pi (60*(pi/15)). Since you evaulate the cosine of angles that are multiples of 4*pi, those answers are all equal to 1 of course,then you multiply each by two.

What are you actually trying to do? Do you want your frequency to be 60 Hz or 60 radians per sample?

I'll assume 60 radians/sample for the moment.

    x = 0:0.001:2*pi;
    y = 2*cos(60*x);
    plot(x,y)

If you want 60 cycles per second

    x = 0:0.001:2;
    y = 2*cos(2*pi*60*x);
    plot(x,y)

[Big Meech]

Hello,

What I'm essentially trying to do is graph the function 2.0*cos(60x) in MATLAB like this: http://www.wolframalpha.com/input/?i=2*cos%2860x%29+graph+from+0+to+3pi

Would I first have to define the 60 in my x vector? I think I know what I have to do now.

Regards