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

[Ryan K. <rk...@si...>]

I think this essentially makes sense, but I use the toolbox with my
undergrads who are new to python.  They might find it annoying to have
to pass in the extra keyword argument toSISO=True every time they
generate a Bode plot or something.  Can we try to intelligently guess
what toSISO should be in the code?  i.e. if the system has only one
input and one output, assume toSISO=True.  We may be able to make this
work by using numpy.squeeze on all array outputs.

Ryan

--
Ryan Krauss, Ph.D.
Assistant Professor
Mechanical Engineering
Southern Illinois University Edwardsville



On Thu, Apr 7, 2011 at 9:56 AM, Richard Murray <mu...@cd...> wrote:
> 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
>>
>>
>> ------------------------
>> Sawyer B. Fuller
>> Ph.D. Candidate, Bioengineering
>> California Institute of Technology
>> http://www.cds.caltech.edu/~minster/
>>
>>
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