Re: [python-control-discuss] call method

[Rene v. P. <ren...@gm...>]

On my experimental branch, I implemented something similar, (but maybe
yours is better), with the method horner (after Scilab's horner). But I
agree that __call__ is a perfectly fine name for this, and I think that we
should simply implement this for both StateSpace and TransferFunction.

I want to vote for keeping it mimo, though

René


On 6 June 2013 23:16, Richard Murray <mu...@cd...> wrote:

> Good call on __call__.  This seems like a fine thing to integrate in.
>
> -richard
>
> On 6 Jun 2013, at 12:36 , Ryan Krauss <rk...@si...> wrote:
>
> > poly1d makes it naturally vectorize so that the __call__ method could
> also be used in Bode-type calculations:
> >
> > In [16]: w = arange(1,5,0.5)
> >
> > In [17]: control.freqresp(test,w)
> > Out[17]:
> > (array([[[ 0.31622777,  0.2981424 ,  0.2773501 ,  0.25607376,
>  0.23570226,
> >           0.21693046,  0.2       ,  0.18490007]]]),
> >  array([[[-0.32175055, -0.46364761, -0.5880026 , -0.69473828,
> -0.78539816,
> >          -0.86217005, -0.92729522, -0.98279372]]]),
> >  array([ 1. ,  1.5,  2. ,  2.5,  3. ,  3.5,  4. ,  4.5]))
> >
> > In [18]: s_vect = 1.0j*w
> >
> > In [18.5]: test(s_vect)
> > Out[18.5]:
> > array([ 0.30000000-0.1j       ,  0.26666667-0.13333333j,
> >         0.23076923-0.15384615j,  0.19672131-0.16393443j,
> >         0.16666667-0.16666667j,  0.14117647-0.16470588j,
> >         0.12000000-0.16j      ,  0.10256410-0.15384615j])
> >
> >
> > In [19]: freq_test = test(s_vect)
> >
> > In [20]: abs(freq_test)
> > Out[20]:
> > array([ 0.31622777,  0.2981424 ,  0.2773501 ,  0.25607376,  0.23570226,
> >         0.21693046,  0.2       ,  0.18490007])
> >
> > In [21]: angle(freq_test)
> > Out[21]:
> > array([-0.32175055, -0.46364761, -0.5880026 , -0.69473828, -0.78539816,
> >        -0.86217005, -0.92729522, -0.98279372])
> >
> >
> >
> > --
> > Ryan Krauss, Ph.D.
> > Associate Professor
> > Mechanical Engineering
> > Southern Illinois University Edwardsville
> >
> >
> > On Thu, Jun 6, 2013 at 2:31 PM, Ryan Krauss <rk...@si...> wrote:
> > FYI, I made this change in my local checkout code and ran a simple test
> and it is working:
> >
> > In [8]: test = control.TransferFunction(1,[1,3])
> >
> > In [9]: s1 = -1+2.0j
> >
> > In [10]: test(s1)
> > Out[10]: (0.25-0.25j)
> >
> > In [11]: 1.0/(s1+3)
> > Out[11]: (0.25-0.25j)
> >
> > Nothing too fancy, but solves my issue.
> >
> >
> > --
> > Ryan Krauss, Ph.D.
> > Associate Professor
> > Mechanical Engineering
> > Southern Illinois University Edwardsville
> >
> >
> > On Thu, Jun 6, 2013 at 1:47 PM, Ryan Krauss <rk...@si...> wrote:
> > I would like to submit some minor patches over the course of the summer
> to help me completely get rid of my old controls module and switch over to
> python-control for everything.  My most immediate need is for a __call__
> method.  This method might not make any sense for a state-space system, but
> for certain aspects of my modeling work, I need to evaluate transfer
> functions at certain numerical values of s.
> >
> > I would propose something like this:
> >
> > def __call__(self, s):
> >     """Evaluate a transfer function at s."""
> >     N_poly = poly1d(squeeze(self.num))
> >     D_poly = poly1d(squeeze(self.den))
> >     return N_poly(s)/D_poly(s)
> >
> >
> > It could also include a check that self is SISO and possibly throw an
> exception if it is not (pretty sure that poly1d will throw one if we pass
> in a vector of coefficients that isn't 1d).
> >
> > Would this be welcome?  Is there anything I should tweak?
> >
> > Thanks,
> >
> > Ryan
> >
> > --
> > Ryan Krauss, Ph.D.
> > Associate Professor
> > Mechanical Engineering
> > Southern Illinois University Edwardsville
> >
> >
> >
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René van Paassen        | ______o____/_|     Ren...@gm...
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