buttLoop error message code lifted from Matlab example 60 Hz hum

Using code from Remove the 60 Hz Hum from a Signal http://www.mathworks.com/help/signal/ug/remove-the-60-hz-hum-from-a-signal.html

plot of filtered data looks reasonable in fig(1)

srate = input ('Enter SAMPLE RATE for this subject(check log book!):    ');   
ChannelFirst = data.ECG;
Fs=srate;
t =( 0:length(data.ECG)-1)/fs;

plot(t,data.ECG);
ylabel 'Voltage (V)', xlabel 'Time (s)'
title 'Open-Loop Voltage with 60 Hz Noise'

d = designfilt('bandstopiir','FilterOrder',2, ...
                'HalfPowerFrequency1',59,'HalfPowerFrequency2',61, ...
                'DesignMethod','butter','SampleRate',Fs);

fvtool(d,'Fs',Fs) ;           

buttLoop = filtfilt(d,openLoop);    ERROR THIS  LINE <===========================

figure (2);
plot(t,data.ECG,t,buttLoop);
 ylabel 'Voltage (V)', xlabel 'Time (s)';
 title 'Open-Loop Voltage', legend('Unfiltered','Filtered');

    [popen,fopen] = periodogram(data.ECG,[],[],Fs);
   [pbutt,fbutt] = periodogram(buttLoop,[],[],Fs);

   plot(fopen,20*log10(abs(popen)),fbutt,20*log10(abs(pbutt)),'--')
   ylabel 'Power/frequency (dB/Hz)', xlabel 'Frequency (Hz)'
   title 'Power Spectrum', legend('Unfiltered','Filtered')

ERROR MESSAGE:

Error in HRcodetest (line 120)
buttLoop = filtfilt(d,openLoop);

[Walter Roberson]

Please include the complete error message, everything in red.

Answer 1

[Star Strider]

Looking at the documentation in the link, ‘openLoop’ is loaded in this line:

load openloop60hertz, openLoop = openLoopVoltage;

and is one of the variables in that .mat file. You have to substitute your own signal, apparently ‘ChannelFirst’, for ‘openLoop’.

[Don]

Thank you! As with my whole life with software, once you know the answer, it's obvious!

[Star Strider]

My pleasure!

I’ve reviewed that example before, so I recognised the problem once I realised you weren’t loading the example data.