Example is wrong => zero-phase filter - filtfilt(ver. 2009a)

http://www.mathworks.com/help/toolbox/signal/filtfilt.html

There is a example y=filtfilt(SOS,G,x) below

but it doesn't match like example

what is the problem?

I want to know in full - fixed full code

For example, about design with butter code or filtfilt code =======================================================

x = ecg(500)'+0.25*randn(500,1); %noisy waveform
h = fdesign.lowpass('N,F3dB',12,0.15);
dl=design(h,'butter');
y=filtfilt(dl.sosMatrix,dl.ScaleValues,x);
plot(x,'b-.'); hold on;
plot(y,'r','linewidth',3);
legend('Noisy ECG','Zero-phase Filtering','location','NorthEast');

========================================================================

please let me know......

[Kaustubha Govind]

Are you saying that running the above code gives you different results from the snapshot in the documentation? If yes, could you post a snapshot of the plot generated on your run?

Note that since you are adding random noise, there may be a small amount of difference in the filtered signal (changes for every run).

Answer 1

[Rob Graessle]

It looks like the documentation for FILTFILT was changed since R2009a. The page you're looking at is the latest documentation (for R2011a). When I run this example in R2009a, it doesn't look right (as you said). But when I run it in R2011a, it looks fine.

Answer 2

[Walter Roberson]

What difference do you see between the calling sequence and the example? dl.sosMatrix would be a SOS (Second Order Section) such as is required for filtfilt()

[Nak]

If you run these codes.. Result disagree from linked site's example result...

so.. need to find wrong coding with detail