Error with Filtfilt line 124 and 67.

Hi everybody, I'm analyzing an EEG but I've encountered some problems. I apply this part of a script:

CR1 = readCRTsd('CSC10.ncs');

dataEEG = resample(Data(CR1), 1, 16);

timeEEG = linspace(StartTime(CR1), EndTime(CR1), length(dataEEG))';

EEG6=tsd (timeEEG,dataEEG);

filelist = dir('CSC*.ncs');

filenames = {filelist.name};

    xl=xlim;

EEG6S2 = Restrict(EEG6, xl(1)*10000, xl(2)*10000);

plot(Range(EEG6, 'sec')-StartTime(EEG6, 's'),Data (EEG6)* 3.05185e-005); % plot in mV% ;

Fs = 1 / median(diff(Range(EEG6, 'sec')));

d = fdesign.bandpass('N,F3dB1,F3dB2', 10, 100, 300, Fs);

H = design(d, 'butter');

EslRipples = filtfilt(H.sosMatrix, H.ScaleValues, Data(EEG6S2));

• * But when I arrive to EslRipples I get this error:

*Error using filtfilt>getCoeffsAndInitialConditions (line 124)
Data must have more than 6 samples.

_ * _ *Error in filtfilt (line 67)
[b,a,zi,nfact,L] = getCoeffsAndInitialConditions(b,a,Npts);

Error in loopcorrelogramandCo (line 13)

EslRipples = filtfilt(H.sosMatrix, H.ScaleValues, Data(EEG6S2));* *

(loopcorrelogramandCo  is my script)** _ * _

What does it mean concretely and how may I solve it? Thanks in advance!

[Geoff Hayes]

Ambra - please format the above code so that is distinct from your question. Highlight the code (and error) portions and press the {}Code button.

As for the error, Data must have more than 6 samples., according to filtfit,

 Note:   The length of the input x must be more than three times the filter  
 order, defined as max(length(b)-1,length(a)-1).

How many samples are you providing to this function? In the Command Window, type (prior to the filtfit call)

 size(Data(EEG6S2))

What do you observe?

[Ambra]

   size(Data(EEG6S2))

ans =

       1     1

I've tried also to check xl(1) and xl(2):

xl(1)

ans =

       0

xl(2)

ans =

       1

But xl derives frome xlim... Is this a problem of the resampling?

[Geoff Hayes]

Ambra - presumably the above code is within a function or script, so you should put a breakpoint at the first line, and step through the code and check the variables. What is the size of CR1, and of the others? Try to figure out whether you have enough samples to begin with, and at what point they are reduced to 1.