[SciPy-User] bug in signal.lsim2

josef.pktd@gmai... josef.pktd@gmai...
Thu Jan 28 15:05:53 CST 2010


On Thu, Jan 28, 2010 at 3:39 PM, Ryan Krauss <ryanlists@gmail.com> wrote:
> I believe I have discovered a bug in signal.lsim2.  I believe the
> short attached script illustrates the problem.  I was trying to
> predict the response of a transfer function with a pure integrator:
>
>              g
> G = -------------
>          s(s+p)
>
> to a finite width pulse.  lsim2 seems to handle the step response just
> fine, but says that the pulse response is exactly 0.0 for the entire
> time of the simulation.  Obviously, this isn't the right answer.
>
> I am running scipy 0.7.0 and numpy 1.2.1 on Ubuntu 9.04, but I also
> have the same problem on Windows running 0.7.1 and 1.4.0.
>
> Thanks,
>
> Ryan

When I add a small noise

u2 = zeros(N) + 1e-14

or for
u2[:50] = amp

or for
u2[50:200] = amp

it seems to work.

This might be a tricky bug.

Josef


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