Re: [python-control-discuss] [BULK] MIMO vs SISO

[Richard M. <mu...@cd...>]

I noticed this change as well.  If you are just using the various functions in python-control, everything works fine (eg, none of the examples had to change).  But if you are extracting frequency responses or otherwise playing with data generated from your system, this is a bit of a hassle.

Here is a proposal:

* For all functions in python-control that accept MIMO systems (all of them eventually), we add two keywords:

  - toSISO=True will force output to be SISO-like (v0.3) if inputs==1, outputs==1
  - toSISO=(n, m) will give you SISO-like output for the nth input to mth output
  - toMIMO=True will force the output to be MIMO-like even if inputs==1, outputs==1

* For the Python interface, the default will be toMIMO=True, so that you get the current behavior.  If you want the scalar version of the outputs, you just add toSISO=True as a keyword.

* For the MATLAB interface, the default will toSISO=True, so that you get MATLAB-like behavior if you extract data from bode(), freqresp(), etc.

One problem with this is that you can have conflicts if you give *both* sets of keywords.  Sometimes this makes sense ("toSISO=(2,3) toMIMO=True"), but sometimes it doesn't ("toSISO=True, toMIMO=True").  So probably needs a bit more thought.  But the idea is that the following code:

  (mag, phase, omega) = bode(sys)
  plot(omega[0][0]), mag[0][0])

becomes

  (mag, phase, omega) = bode(sys, toSISO=True)
  plot(omega, mag)

which I think is a bit cleaner.

Comments, suggestions?

-richard



On 6 Apr 2011, at 14:19 , Sawyer Fuller wrote:

> Hey i just downloaded the latest version of python-control and it looks like everything has gone MIMO. Pretty cool, but is there any way to way to stick to SISO, eg a subclass or flag? A little bit of a drag to constantly be appending [0][0] to every frequency response for the most common use case. I think matlab does a special-case for SISO. Anything like that in the works or somewhere i'm not finding it? 
> 
> S
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> ------------------------
> Sawyer B. Fuller
> Ph.D. Candidate, Bioengineering
> California Institute of Technology
> http://www.cds.caltech.edu/~minster/
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