Re: [python-control-discuss] really weird error for SISO step response

I just ran a pip upgrade for the control module.  I am running 0.8.2.

I just tried upgrading slycot via pip.  pip says I am currently running
0.3.0.  I tried to upgrade to 0.3.5 via pip, but I receive error messages
about gfortran and xcode.  I am kind of surprised that I don't have them
both working.  I will work on that.

I am getting False for this variable: slycot.__SLYCOT_SETUP__

--
Dr. Ryan Krauss
Associate Professor
Product Design and Manufacturing Engineering
Grand Valley State University


On Fri, Aug 30, 2019 at 2:16 AM Murray, Richard M. <mu...@cd...>
wrote:

> Which version of python-control and slycot?  I just ran against the latest
> master and slycot 0.3.4 and it didn’t generate an error.
>
> -richard
>
> > On 29 Aug 2019, at 11:04 , Ryan Krauss <kra...@gv...> wrote:
> >
> > I am trying to do a super basic step response for a first order TF and
> am getting an error I have never seen before.  The notebook is attached,
> but here is the code and the error message:
> >
> > %matplotlib inline
> > import matplotlib.pyplot as plt
> > import numpy as np
> > import control
> > from numpy import sin, cos, tan, pi
> > from control import TransferFunction as TF
> >
> > p = 30
> >
> > G = control.TransferFunction(p,[1,p])
> > G
> >
> > control.step_response(G)
> >
> >
> ---------------------------------------------------------------------------
> > ValueError
> >                                 Traceback (most recent call last)
> >
> > <ipython-input-7-7235fbf92fdd> in <module>()
> > ----> 1 control.step_response(G)
> >
> >
> >
> > /usr/local/lib/python3.6/site-packages/control/timeresp.py in
> step_response(sys, T, X0, input, output, transpose, return_x)
> >     450     >>> T, yout = step_response(sys, T, X0)
> >     451
> >      """
> >
> > --> 452     sys = _get_ss_simo(sys, input, output)
> >     453     if T is None:
> >     454         if isctime(sys):
> >
> >
> >
> > /usr/local/lib/python3.6/site-packages/control/timeresp.py in
> _get_ss_simo(sys, input, output)
> >     378     If input is not specified, select first input and
> >  issue warning
> >
> >     379
> >      """
> >
> > --> 380     sys_ss = _convertToStateSpace(sys)
> >     381     if sys_ss.issiso():
> >     382         return
> >  sys_ss
> >
> >
> > /usr/local/lib/python3.6/site-packages/control/statesp.py in
> _convertToStateSpace(sys, **kw)
> >     895             # transfer function to state space conversion now
> should work!
> >     896
> >              ssout = td04ad('C', sys.inputs, sys.outputs,
> >
> > --> 897
> >                             denorder, den, num, tol=0)
> >
> >     898
> >
> >
> >     899             states = ssout[0]
> >
> >
> >
> > /usr/local/lib/python3.6/site-packages/slycot/transform.py in
> td04ad(rowcol, m, p, index, dcoeff, ucoeff, tol, ldwork)
> >     446         e = ValueError(error_text)
> >     447         e.info = out[-1]
> > --> 448         raise
> >  e
> >
> >     449     if out[-1] > 0:
> >     450         error_text = "The leading coefficient of a denominator
> polynomial is nearly zero; calculations would overflow; no state-space
> representation was calculated.
> ABS(DCOEFF("+str(out[-1])+",1))="+str(abs(dcoeff(out[-1],1)))+" is too
> small."
> >
> >
> >
> > ValueError: The following argument had an illegal value: dcoeff
> >
> > --
> > Dr. Ryan Krauss
> > Associate Professor
> > Product Design and Manufacturing Engineering
> > Grand Valley State University
> > <illegeal_dcoeff.ipynb>_______________________________________________
> > python-control-discuss mailing list
> > pyt...@li...
> > https://lists.sourceforge.net/lists/listinfo/python-control-discuss
>
>
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