when i try to run ''N =length(EEGsig);'' i am getting this ''Undefined function or variable 'EEGsig'.'' error... please help me how to solve this problem

fs = 512
 T = 1/fs;
 N =length(EEGsig); ls = size(EEGsig);
 tx =[0:length(EEGsig)-1]/fs;
 fx = fs*(0:N/2-1)/N;
 x=  EEGsig;    
 sd = 0.1;                                       
 normal_noise = sd*randn(1, N);
 noisy_EEGsig = x + normal_noise;
 figure();    
 subplot(4,1,1);
 grid on;  
    
 plot(tx, x);
 xlabel('Time [s]');                                                        
 ylabel('Amplitude');
 title('Original signal');
 subplot(4,1,2);
 grid on;  
 plot(tx,normal_noise);
 xlabel('Time [s]');
 ylabel('Amplitude');
 title('Noise');
 subplot(4,1,3);
 grid on;
 plot(tx, noisy_EEGsig);
 xlabel('Time [s]');
 ylabel('Amplitude');
 title('Original signal + Noise'); 
 subplot(4,1,4);
 d = designfilt('bandstopiir', 'FilterOrder', 2, 'HalfPowerFrequency1', 59, 'HalfPowerFrequency2', 61, 'DesignMethod', 'butter', 'SampleRate', fs);
 fvtool(d,'fs',fs)  
 buttLoop = filtfilt(d, noisy_EEGsig);
 plot(t, noisy_EEGsig,t,buttLoop)
 ylabel('Voltage (V)')
 xlabel('Time (s)')
 title('filtered signal')
 legend('Unfiltered','Filtered')
 grid

Answer 1

[Walter Roberson]

There is no Mathworks function or built-in data set by that name. You need to load some eeg data from somewhere and assign it to that variable.

[S Buvanesh Bharathwaj]

how to do that sir.... can u tell the code for doing that process

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/126424-reading-eeg-signals-taken-from-physionet-org#comment_341681