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 PackageSeverity: 3 - Normal
Priority: 1 - LaterItem Group: Matlab Compatibility
Status: PostponedAssigned to: None
Originator Name: Tony RichardsonOriginator Email: -unavailable-
Open/Closed: OpenRelease: 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
    Tue 03 Apr 2018 07:24:47 AM UTCmtmillerPriority5 - Normal=>1 - Later
    Wed 21 Mar 2018 01:19:39 AM UTCmtmillerStatusNeed Info=>Postponed
      Operating SystemMicrosoft Windows=>Any
    Thu 19 Oct 2017 07:10:50 PM UTCmtmillerStatusNone=>Need Info
      Summaryfiltic output not compatible with MATLAB=>[octave forge] (signal) filtic output not compatible with MATLAB

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