I am using a butterworth filter (scripted below) and the script jams with this error response

[b,a] = butter(4,10/120,'low');

Undefined function or variable 'RTROx'.

Error in angle (line 26) RTROx = filtfilt(b,a,RTROx);

This script ran fine on o 2011 version. I downloaded 2012 with signal processing toolbox - so think I have all that I need, but am left to wonder why the error...

Answer 1

[Honglei Chen]

Hi Katherine,

Is the result of

which butter

same for both installations? It sounds like you have a custom butter on path.

[Katherine Whitcome]

Hi and thanks for your reply.

I do get the same result for both installations:

/Applications/MATLAB_R2011b.app/toolbox/signal/signal/butter.m

[Honglei Chen]

That's weird. I don't think butter calls filtfilt at all. It looks like RTTOx is not defined. Are you sure the error is thrown by the butter command?

BTW, in the future you may want to wait till the problem resolved to accept the answer. The accepted answer suppose to be the answer that solves your issue.

Answer 2

[Star Strider]

I suggest:

which angle

as well. The 'angle' function I know and love takes a complex argument and computes a phase angle from it. To the best of my knowledge, it doesn't call 'flitfilt' either.