Plotting cos(omega*t)?

Hi, How do you plot cos(omega*t) where omega=2*pi*f, for range of frequency like (20:2000). I am confused because there is both time and frequency, do we need to convert time to frequency domain?

Answer 1

[Jos (10584)]

This might guide you a little:

t = linspace(0,10,1000) ; % time vector 
f = 20 ; % a frequency
omega = 2.*pi.*f ; % calculate omega
y = cos(omega.*t) ;       % calculate cosine for this time span
plot(t,y)  % plot it

(btw, I prefer to use the .* notation for multiplication)

[shashank]

is it possible to plot with frequency varying from 20:2000 hz for example with x axis as frequency? i am not certain that i need to do FFT

[Steven Lord]

If you're using plot you have two axes so you can plot {something} versus {something else}. For {something} you want to use frequency; is {something else} t or y? Or do you want to create a 3-D plot where the X axis corresponds to frequency, Y axis to time, and Z axis to the value of the variable y?

[shashank]

so i have this function f=cos(w*t), i want to plot in 2D (in frequency domain) with x axis as frequency and magnitude in y axis do i need to do FFT? if x axis ranges from 20:2000

[Jos (10584)]

the magnitude does not change with the frequency ... Or do you mean something else?

[shashank]

This is exactly what i wanted to knw, so magnitude do not change with frequency for f=cos(w*t)?