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Correctly combine zpk systems#34

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Correctly combine zpk systems#34
MitchellThompkins wants to merge 1 commit into
gnu-octave:devfrom
MitchellThompkins:mitchellthompkins/combine-zpk-systems

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@MitchellThompkins MitchellThompkins commented Jul 13, 2026

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Description

#31 (comment) pointed out that

the combination (series, feedback) of two systems represented in zpk form results in a system in tf form

This is of course wrong and I've tried to address it here. While addressing I also realized a number of functions were also returning tf data types because they delegate to tf. That's of course also wrong because when you work with zpk you should expect to stay in that data type (even if the backing implementation degrades to another system representation).

Changes

  • For all the new zpk data types they all actually return zpk.
  • __times__ (.*), __sys_group__ (+) now return the correct types and data shape (I think)
  • Added more tests to tests all of these things

@MitchellThompkins MitchellThompkins marked this pull request as draft July 13, 2026 06:31
@MitchellThompkins MitchellThompkins force-pushed the mitchellthompkins/combine-zpk-systems branch from 9f3567b to e5a5992 Compare July 13, 2026 06:46
@MitchellThompkins MitchellThompkins marked this pull request as ready for review July 13, 2026 06:48
@MitchellThompkins MitchellThompkins changed the title Add tests for zpk functions that combine systems Correctly combine zpk systems Jul 13, 2026
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