bugGNU Octave - Bugs: bug #52254, [octave forge] (signal) filtic...


bug #52254: [octave forge] (signal) filtic output not compatible with MATLAB

Submitted by:  None
Submitted on:  Thu 19 Oct 2017 07:01:38 PM UTC  
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  1 - Later Item Group:  Matlab Compatibility
Status:  Postponed Assigned to:  None
Originator Name:  Tony Richardson Originator Email:  -email is unavailable-
Open/Closed:  Open Release:  other
Operating System:  Any

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Wed 21 Mar 2018 01:19:39 AM UTC, comment #1:

A solution that works equally well is to divide the output by a(1) before returning from filtic.

I don't know at the moment what the right solution here is. But I can confirm that a(1) is never used inside the function as it is written currently.

Mike Miller <mtmiller>
Project Administrator
Thu 19 Oct 2017 07:01:38 PM UTC, original submission:

I was getting incorrect results using the filter function. I tracked the issue down to a problem with filtic.

b = [4 -3]; a = [2 -3 1];
filtic(b, a, [0 1])

returns [-1 0] as a result. The correct result (and that returned by MATLAB) is [-0.5 0].

Octave returns the MATLAB result if I divide both b and a by a(1):

b = [4 -3]; a = [2 -3 1];
filtic(b/a(1), a/a(1), [0 1])

gives [-0.5 0].

An easy fix is to divide both vectors by a(1) inside the filtic function, but I am not sure that is the best solution.



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    Follow 6 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2018-04-03 mtmiller Priority5 - Normal => 1 - Later
    2018-03-21 mtmiller StatusNeed Info => Postponed
        Release4.2.1 => other
        Operating SystemMicrosoft Windows => Any
    2017-10-19 mtmiller StatusNone => Need Info
        Summaryfiltic output not compatible with MATLAB => [octave forge] (signal) filtic output not compatible with MATLAB

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