[Octave-bug-tracker] [bug #61355] Error on phase value of bode and margin plots

[Luiz Antonio Maccari Junior]

Follow-up Comment #4, bug #61355 (project octave):

I am posting two additional examples of error in margin and bode functions.

Example 4 in file "bug_report_bode_ex4.m".

The bode plot of matlab and octave are the same both are correct. However, the
margin function is incorrect in octave. The phase plot in octave margin phase
plot starts in +180 and it should be -180.
See files: matlab_output_margin_ex4.jpg and octave_output_margin_ex4.jpg


Example 5 in file "bug_report_bode_ex5.m".

Here the bode function phase plot is wrong. It should start with 0 degree but
it is starting with +180.

Sometimes the phase plot is wrong in bode function and sometimes is wrong in
margin function. In margin function the error also leads to an error on gain
margin. It seems that the error is in the wrapping of the phase plot. In
example 5 bode function plotted a wrong phase range and in example 4 the error
is in the phase range of margin function.

As I mentioned before, Matlab does not put wrap as default giving an option to
choose it. Also in matlab it is important to note that the wrapping does not
interfere on the results of gain or phase margin.

Thank for your time.   



(file #52130, file #52131, file #52132, file #52133)
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Additional Item Attachment:

File name: bug_report_bode_ex4.m          Size:0 KB
    <https://file.savannah.gnu.org/file/bug_report_bode_ex4.m?file_id=52130>

File name: matlab_output_margin_ex4.jpg   Size:22 KB
   
<https://file.savannah.gnu.org/file/matlab_output_margin_ex4.jpg?file_id=52131>

File name: bug_report_bode_ex5.m          Size:0 KB
    <https://file.savannah.gnu.org/file/bug_report_bode_ex5.m?file_id=52132>

File name: octave_output_margin_ex4.jpg   Size:55 KB
   
<https://file.savannah.gnu.org/file/octave_output_margin_ex4.jpg?file_id=52133>



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