how to plot the magnitude of x(k) in matlab

x(k)= 4j exp(-6*pi*j*k/N)

where 0 <= k <= N-1 and x(k) be N-point DFT of the length N sequence

[Birdman]

The question is not clear. Be more specific.

Answer 1

[Rik]

You already have a function, you just need to calculate the magnitude, which is just the abs function. The thing is, you can see beforehand that this is a useless exercise, because it will always be 4. The exponent part doesn't influence the magnitude, so k has no influence on the magnitude.

N=20;
x_mag=@(k) abs(4j*exp(-6*pi*1j*k/N));
fplot(x_mag,[0,N-1])

(you can also use linspace and plot)

[Aash]

thanks very much for your help and explanation.