spectrum analysis

clc;close all;clear all;
%% ------------------------------------------------------------------------
disp('Spectrum Analysis of DFT')
disp('Tarun Shrivastava - TETA14')
disp('Execution date - 24 Jan,2020')
%% --------------------Implementation of formula for DFT-------------------
x=[1 1 1 1];
subplot(3,3,1)
stem(x)
grid on
for i=2:1:9;
    N=2^i  ;
% N=input('Enter no. of DFT points');      % N=4;
% x=input('Enter DFT samples');            %x=[1 1 1 1];
    n=[0:1:(N-1)];
    k=[0:1:(N-1)];
    l=length(x);
    if(N>l)
        x=[x zeros(1,(N-l))];
    elseif(N<l)
        x=x(1:N);
    end
    w=exp((-1j*2*pi*n'*k)/N);
    X=w*x';
    subplot(3,3,i)
    stem(X)
    grid on    
end