Problem with toolbox filter design?

Hi everybody, I need help with disigning filters in matlab:

I was designed a bandpass filter in the toolbox and export it like an object to my workspace, then I tried to filter data with it using the comand filtfilt, the problem es that this comand don't recognize this filter as a matrix so when i use the follow linecommand: a11=filtfilt(Fil1,a1); i recived the follow error "Not enough input arguments". The Fs frecuency of the filter is 1000Hz, the Flowpass is 10Hz and the Fhighpass is 14Hz. Apass 1dB. Type Chebychev Type 1.

thanks

Answer 1

[Wayne King]

Assume that Fil1 is your filter object, if you enter

 class(Fil1)

does it return dfilt.df2sos?

If so, then depending on what version of MATLAB you are using, try:

out = filtfilt(Fil1.sosMatrix,Fil1.ScaleValues,a1);

where a1 is your data.

If you have an older version of MATLAB where the above command does not work, write back.

[Stefan Leiva]

Hi Wayne, when I wrote the command all the vector out is fill with NaN values, when I wrote Fil1.sosMatrix shows: >> Fil1.sosMatrix

ans =

    1.0000         0   -1.0000    1.0000   -1.9964    0.9973
    1.0000         0   -1.0000    1.0000   -1.9987    0.9993
    1.0000         0   -1.0000    1.0000   -1.9978    0.9990
    1.0000         0   -1.0000    1.0000   -1.9973    0.9980
    1.0000         0   -1.0000    1.0000   -1.9965    0.9976
and when I wrote 
 Fil1.ScaleValues

ans =

    0.0001
    0.0011
    0.0109
    0.0018
    0.0083
   19.7438

What can i do?

thanks.

[Wayne King]

Did the command at least run? It did not throw an error?

Do you have NaNs in your data? If you have any NaNs in your data, then you will only get NaNs out.

[Stefan Leiva]

I don´t have NaNs in my data. When I use the command Filter, it works, my problem is that the filter comand moves the response (filter data), I think that it could be becouse of the phase angle. I want to try with this comand.

[Wayne King]

That is strange because I don't have any trouble with your filter. Can you try this:

n = 0:499;
x = cos(0.01*pi*n)+sin(pi/4*n)+randn(size(n));
y = filtfilt(Fil1.sosMatrix,Fil1.ScaleValues,x);

Do you get NaNs in your output with the above?

[Stefan Leiva]

with your answer also have Nans, can I send you the folder with all my data?, I think it´s strange too. the link with data is https://www.dropbox.com/s/gtp3k9g5cygjpru/Puente%20San%20Luis%2001-P-012%20K14%2B378.zip. Thanks

[Wayne King]

Are you using the MathWorks' version of filtfilt()? If you enter

>>which filtfilt

what do you get returned?

[Stefan Leiva]

it is what it returns: C:\Program Files\MATLAB\R2008a\toolbox\signal\signal\filtfilt.m