bugGNU Octave - Bugs: bug #53011, Documentation of sort and...

 
 

bug #53011: Documentation of sort and comparison operators

Submitter:  Michael Leitner <mleitner>
Submitted:  Tue 30 Jan 2018 10:22:07 AM UTC
   
 
Category:  Octave Function Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Documentation
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * 4.2.1 Operating System:  * Any
Fixed Release:  None Planned Release:  None
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Tue 30 Jan 2018 10:22:07 AM UTC, original submission:  

I am splitting up bug #52919. First the smallest issue, that I called a buglet there:

According to the documentation of sort: Sorting of complex entries is done first by magnitude ('abs (Z)') and for any ties by phase angle ('angle (z)'). However, consider the following code:


a=complex([-5; 0; 5;0;-5],[+0;5; 0;-5;-0])
abs(a)==5
angle(a)
angle(sort(a))


That is, all entries have the same length and thus should be sorted according to angle. But they are not due to inconsistent treating of +0i and -0i on the negative axis. This is due to the comparison on complex values:


a<=5


As Rik noted in comment 14 of #52919, if in the comparison an angle of -pi appears, it is mapped to +pi. So this is a documentation bug for sort and the comparison operators, of course only of low priority.

Michael Leitner <mleitner>

 

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