bugGNU Octave - Bugs: bug #54424, [octave forge] (signal) filtfilt...


bug #54424: [octave forge] (signal) filtfilt only accepting input arrays of length > 3*N

Submitted by:  Arnaud Delorme <arnodelorme>
Submitted on:  Wed 01 Aug 2018 11:04:04 PM UTC  
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Unexpected Error
Status:  Fixed Assigned to:  None
Originator Name:  Open/Closed:  Closed
Release:  4.4.0 Operating System:  Mac OS

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Tue 14 Aug 2018 05:15:44 AM UTC, comment #5:

I improved the error reporting for this situation


This fix will be part of the next release of the signal package.

Mike Miller <mtmiller>
Project Administrator
Thu 02 Aug 2018 02:05:11 AM UTC, comment #4:

Yes, on Matlab, the error is

Error using filtfilt>getCoeffsAndInitialConditions (line 182)
Data length must be larger than 48 samples.

On Octave

error: x(49,_): but x has size 48x1
error: called from
filtfilt at line 75 column 7

Arnaud Delorme <arnodelorme>
Thu 02 Aug 2018 01:20:52 AM UTC, comment #3:

Not necessary. If the error is reported better in Matlab, then we could have a clearer error message in Octave that the size of the input vector is too small.

Mike Miller <mtmiller>
Project Administrator
Thu 02 Aug 2018 01:17:04 AM UTC, comment #2:

Yes, Matlab has the same behavior.

I have a test case on Matlab that failed on Octave, and I thought this was the issue. I can dig further if necessary but otherwise, I will let it go.


Arnaud Delorme <arnodelorme>
Thu 02 Aug 2018 01:11:19 AM UTC, comment #1:

Confirmed, apparently the current implementation assumes that the length of the signal X is at least 3 times the length of the order of the filter. With your example of a 16th order filter, the code assumes the signal is at least 3*16+1.

Mike Miller <mtmiller>
Project Administrator
Wed 01 Aug 2018 11:04:04 PM UTC, original submission:


return an error


works fine. Probably a rounding issue somewhere.

Arnaud Delorme <arnodelorme>


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2018-08-14 mtmiller StatusConfirmed => Fixed
        Open/ClosedOpen => Closed
    2018-08-02 mtmiller StatusNone => Confirmed
        Summaryfiltfilt only accepting input arrays of specific length => [octave forge] (signal) filtfilt only accepting input arrays of length > 3*N

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