《DSP using MATLAB》示例Example5.1

xn = [0, 1, 2, 3]; N =4; 
Xk = dfs(xn,N)

function [Xk] = dfs(xn,N)
%% Computes Discrete Fourier Series Coefficients
%% ---------------------------------------------
%% [Xk] = dfs(xn,N)
%% Xk = DFS coeff. array over 0 <= k <= N-1
%% xn = One period of periodic signal over 0 <=n <= N-1
%%  N = Fundamental period of xn
%% 
n = [0:1:N-1];                     % row vector for n
k = [0:1:N-1];                     % row vector for k
WN = exp(-j*2*pi/N);               % Wn factor
nk = n‘*k;                         % creates a N by N matrix of nk values
WNnk = WN .^ nk;                   % DFS matrix
Xk = xn * WNnk;                    % row vector for DFS coefficients