alias.m

T=5;                              % fundamental period
Np   = 512;                       % number of points for plotting
t=linspace(0,T,Np+1);t=t(1:Np);   % fine resolution time, for plotting
N= 16;                            % number of sampling points
Ts = T/N;                         % sampling interval
fs = 1/Ts;                        % sampling frequency
ts = Ts*(0:(N-1));                % instants when sampling accours
Nf = 1/(2*Ts);                    % Nyquist frequency

f  = k/T;                         % true frequency of the signal
x  = sin(2*pi*f*t);               % signal, high resolution
xs = sin(2*pi*f*ts);              % signal, sampling resolution

% find fapp, such that f=n*fs+fapp
n    = round(f/fs);
fapp = f-n*fs;
xa   = sin(2*pi*fapp*t);

plot(t,[x;xa],ts,xs,'o');
str1 = ['fs=',num2str(fs),' Nf=',num2str(Nf)];
str2 = ['k=',num2str(k),'  f=',num2str(f),'   fapp=',num2str(fapp)];
str  =[str1, '   ',str2];
title(str);