How can I plot a frequency spectrum in MatLab

I wanted to know how I can plot a frequency spectrum, with the data provided from the following code. Basically I am trying to see if the EEG threshold is above or below a certain threshold.

clc
clear all
close all

%Convert data from edf to Matlab
[header, data] = edfread('Subject2.edf');
fs = 128; % sampling rate of Emotiv EEG 

%averaging to remove common noise
for i=1:14
   datan(i,:)=data(i+2,:)-mean(data(3:16,:));
end

fmin  = 30;  % minimum passband frequency in Hz (High Gamma)
fmax  = 50;  % maximum passband frequency in Hz (High Gamma)
Rs    = 20; % stopband attenuation in dB
Rp    = 1;  % passband ripples in dB

% for High gamma band 
[order, Wn] = ellipord([fmin/(fs/2), fmax/(fs/2)], [(fmin-1)/(fs/2), (fmax+1)/(fs/2)], Rp, Rs);
[B,A] = ellip(order, Rp, Rs, [fmin/(fs/2), fmax/(fs/2)]); 

%filtering of entire data into High Gamma band
data_hgamma = filtfilt(B,A,datan');

%segment - extract only the eeg when subject was listening to words using marker data from channel 36
%don't forget to keep the low noise and high noise data separate
val49=find(data(36,:)==49);
val50=find(data(36,:)==50);
val51=find(data(36,:)==51);
val52=find(data(36,:)==52);

for j=1:14
    for i=1:96
    EEG_hgamma(j,i,:)=data_hgamma(val50(i):0.5*128-1+val50(i),j);
    end
end

%0 less noise, 1 more noise
noise_array = [1 0 0 0  0 1 0 1  0 1 0 1  1 1 0 0  0 1 0 1  1 1 0 0  0 1 0 1  1 1 0 0  0 1 0 1  0 0 0 0  1 1 1 1  1 1 0 1  0 0 0 0  0 0 0 0  1 1 0 0  0 1 0 0  1 0 0 0  0 0 1 1  1 0 0 0  1 0 0 0  0 1 1 0  1 0 1 0  1 0 0 1  1 0 1 1];

p=1; q=1;
for i=1:96
    if(noise_array(i)==0)
         EEGL_hgamma(:,p,:)= EEG_hgamma(:,i,:);
         p=p+1;
    else
         EEGH_hgamma(:,q,:)= EEG_hgamma(:,i,:);
         q=q+1;
    end
end

%%%%%%%%write script for noisy EEG data removal

for j=1:14
    for i=1:size(EEGH_hgamma,2)
    Energy_EEGH(j,i)=var(EEGH_hgamma(j,i,:));
    end
end

for j=1:14
    for i=1:size(EEGL_hgamma,2)
    Energy_EEGL(j,i)=var(EEGL_hgamma(j,i,:));
    end
end

for j=1:14
[P(j),H(j),STATS(j,:)] = ranksum(Energy_EEGH(j,:),Energy_EEGL(j,:),'tail','right')
end

Answer 1

[Star Strider]

I’m not sure what you want to plot. I would use the approach in this documentation for the fft function.