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

[Stefan van der Walt]

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])

Cheers
Stéfan