How can i filter an EEG signal?

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Aparna Gupta
Aparna Gupta 2017-7-8
编辑： Walter Roberson 2017-10-24
I have generated an EEG signal in MATLAB.Then in have added random noise to it,n then filtered it using the code as under.But i am getting an error.Can anyone help me to remove it ?
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
The error i am getting is :
"Undefined function 'designfilt' for input arguments of type 'char'."
  1 个评论
aida
aida 2017-10-24
your error in this line (9.noisy_EEGsig = x + normal_noise) and error because of sum different matrix with each other and the correct on is noisy_EEGsig = tx + normal_noise

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采纳的回答

Star Strider
Star Strider 2017-7-8
Three possibilities:
1. You do not have the Signal Processing Toolbox (that has the designfilt function);
2. Your MATLAB and Signal Processing Toolbox versions are prior to R2014a when designfilt was added;
3. You have an appropriate version of the Signal Processing Toolbox, and need to run these commands (from your Command Window or a script) to restore the correct paths:
restoredefaultpath
rehash toolboxcache
Note that no frequency-selective filter will completely eliminate broad-band noise, and a bandstop filter of the sort you want to implement will only eliminate 60 Hz mains frequency noise.

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