i want to write matlab code that calculates fourier transform of following sequence and also plots its magnitude x(k)

x(n) = 3cos(4*pi*n/N) + sin(6*pi*n/N) where 0 <= n=< N-1 0 <= k =< N-1

Answer 1

[Birdman]

N=100;%%you can change it
n=0:N-1;
x=3*cos(4*pi*n/N)+sin(6*pi*n/N);
FFT=fft(x);
plot(abs(FFT))

Also please check

help fft

[Aash]

thanks

[Aash]

but what if i have to plot both real and imaginary components seprately?

[Birdman]

You can not plot imaginary parts. The purpose of fft is to see the signals behaviour in frequency domain and by taking abs command, you make the signal appropriate for fft. The magnitude as you say in your question is relevant and we need to find the magnitude of the signal.

[Aash]

ok.. Thanks