bugGNU Octave - Bugs: bug #53649, [octave forge] (control) tf could...

 
 

bug #53649: [octave forge] (control) tf could be more tolerant to complex coefficient

Submitter:  Charles Praplan <charprap>
Submitted:  Sat 14 Apr 2018 07:35:22 AM UTC
   
 
Category:  Octave Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Missed Error or Warning
Status:  Fixed Assigned to:  None
Originator Name:  Charles Praplan Open/Closed:  * Closed
Release:  * 4.2.2 Operating System:  * Microsoft Windows
Fixed Release:  None Planned Release:  None
* Mandatory Fields

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Discussion

Sat 24 May 2025 07:34:23 AM UTC, comment #5: 

Complex coefficients in a transfer function (with a warning message) are implemented in the current dev branch of the control package and will be part of the 4.2.0 release of the package.

Torsten Lilge <ttl>
Group Member
Sun 15 Apr 2018 10:24:13 AM UTC, comment #4: 

Yes, same behavior as Matlab will be fine.

Charles Praplan <charprap>
Sat 14 Apr 2018 08:25:21 PM UTC, comment #3: 

This is the complete output:

Warning: The numerator or denominator of this transfer function has complex-valued coefficients.

> In tf (line 360)


SYS =
 
     (0.253+1e-18i)
  ---------------------
  z^2 - 1.158 z + 0.411
 
Sample time: 0.0001 seconds
Discrete-time transfer function.

Alexander Wilms <alexanderw>
Sat 14 Apr 2018 08:19:57 PM UTC, comment #2: 

Output of Matlab R2018a:

Warning: The numerator or denominator of this transfer function has complex-valued coefficients.

Alexander Wilms <alexanderw>
Sat 14 Apr 2018 08:55:31 AM UTC, comment #1: 

How tolerant do you want it?
What does matlab do?

Doug Stewart <dastew>
Sat 14 Apr 2018 07:35:22 AM UTC, original submission:  

Function tf could be more tolerant to complex coefficients in case of residual imaginary part due to arithmetic rounding.

See example below.

A warning would be better.

SYS=tf([0 0 0.253+j*1e-18] , [1, -1.158, 0.411], 1e-4)

Charles Praplan <charprap>

 

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    History

    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2025-05-24 ttl StatusNeed Info Fixed
        Open/ClosedOpen Closed
    2018-04-14 mtmiller CategoryLibraries Octave Package
        StatusNone Need Info
        Summarytf could be more tolerant to complex coefficient [octave forge] (control) tf could be more tolerant to complex coefficient

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