# Plotting results of DFT loop

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Alexandr Lozak on 23 Sep 2019
Answered: Guru Mohanty on 13 Jan 2020
I am trying to make multiple DFT from the code of single DFT. But cant figure out how to change plot inputs to see results as it was for single DFT.
%% Plotting single graph of DFT
va= DifVD(1:end); %DifDr(ss(1):ss(2),1);%
y = va; %the signal you want to fft
L = length(y);
Fs=10;
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y = fft(y,NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
% Plot single-sided amplitude spectrum.
fg=figure('Renderer', 'painters', 'Position', [100 100 700 500]);
plot(f,2*abs(Y(1:NFFT/2+1))) % semilogx(f,2*abs(Y(1:NFFT/2+1)))%
%% Plotting multiple graphs of DFT
ss=300000:6000:525158;
k=length(ss);
for i=1:k
va(:,i)= DifDr(ss(i):ss(i+1),1);
y = va;
L = length(y(1));
Fs=10;
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
Y(:,i) = fft(y(:,i),NFFT)/L;
f = Fs/2*linspace(0,1,NFFT/2+1);
% Plot single-sided amplitude spectrum.
fg=figure('Renderer', 'painters', 'Position', [100 100 700 500]);
plot(f,2*abs(Y(1:NFFT/2+1,i)))
end
How should i change last line to plot multiple results?

KALYAN ACHARJYA on 23 Sep 2019
Multiple DFT with respect to whcih parameters (In this multiple inputs)?
Alexandr Lozak on 24 Sep 2019
In general it should look like
plot(f, Y(1:NFFT/2+1,i));
but i dont understand why it doesnt work for many plots

Guru Mohanty on 13 Jan 2020
Hi, it is difficult to provide an exact solution without your original data. However, when I executed your code using random data, at last iteration it is trying to access beyond the last element. After modifying the loop parameter, the code should work.
clc;
clear all;
DifDr=randi(100,525158,5); % Demo data
ss=300000:6000:525158;
k=length(ss);
for i=1:k-1
va(:,i)= DifDr(ss(i):ss(i+1),1); %
y = va;
[L , ~]= size(y);
Fs=10;
NFFT = 2^nextpow2(L); % Next power of 2 from length of y
f = Fs/2*linspace(0,1,NFFT/2+1);
Y(:,i) = fft(y(:,i),NFFT)/L;
% Plot single-sided amplitude spectrum.
fg=figure('Renderer', 'painters', 'Position', [100 100 700 500]);
plot(f,2*abs(Y(1:NFFT/2+1,i))); % semilogx(f,2*abs(Y(1:NFFT/2+1)))%
end