Re: [python-control-discuss] call method

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

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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