# [SciPy-user] problems with signal-functions impulse and step ...

Stef Mientki S.Mientki@ru...
Mon Apr 16 03:01:14 CDT 2007

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Stefan van der Walt wrote:
> Hi Stef
>
> On Sun, Apr 15, 2007 at 10:35:12PM +0200, Stef Mientki wrote:
>
>> I wonder if I'm doing something wrong,
>> or if the signal library might have has some small bugs.
>> Do others have the same experience ?
>>
>> #I create a highpass filter,
>> #which amplitude and phase characteristic looks good
>> filt_1 = signal.iirdesign( 0.06, 0.002, 1, 50, 0, 'butter')
>>
>> # Now when I want to calculate the impuls response,
>> aa,bb = signal.impulse( filt_1[0], filt_1[1] )
>>
>
> The function signature for signal.impulse is
>
> signal.impulse(system, X0=None, T=None, N=None)
>
> Where
>
>       system -- an instance of the LTI class or a tuple with 2, 3, or 4
>                 elements representing (num, den), (zero, pole, gain), or
>                 (A, B, C, D) representation of the system.
>
> (By the way, IPython is extremely useful in investigating this sort of
> thing -- you simply type signal.impulse?<enter>)
>
> So, I think what you want to do is:
>
> aa,bb = signal.impulse(filt_1[:2])
>
>
thanks Stéfan,
but it doesn't seem to work either.

Although I'm just a beginner with Python (coming from MatLab),
I don't see the difference between:

aa,bb = signal.impulse(filt_1[:2])

aa,bb = signal.impulse(filt_1)

knowing that the first dimension of filt_1 = 2,

and indeed it gives the same problems ;-)

or am I missing something ?

cheers,
Stef

Kamer van Koophandel - handelsregister 41055629  / Netherlands Chamber of Commerce - trade register 41055629

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