On Jan 12, 2013, at 2:28 PM, Andre Holzner <[email protected]> wrote:

Hi,

thanks for the prompt reply and the workaround !

On Saturday, 12 January 2013 20:45:40 UTC+1, Aaron Meurer wrote:
>
> First off, why do you use Lambda. Just use Max(x, 5).
>
> This is definitely a bug.


Should I open a ticket ?


Yes, please.



> You can work around it by wrapping x in
> re(), like plot(Max(re(x), 5)).


in fact, doing

plot(Max(re(x),5), (x,0,10))


Hmm. This worked for me.

Aaron Meurer


I get the same exception (originating at the same place)

while

plot(re(Max(x,5)), (x,0,10))

works.

thanks,

Andre




> Perhaps plot should automatically do
> this if x is assumed to be real.  Even so, it should not have this
> error regardless of assumptions.
>
> Aaron Meurer
>
> On Sat, Jan 12, 2013 at 11:53 AM, Andre Holzner 
> <[email protected]<javascript:>>
> wrote:
> > Dear sympy experts,
> >
> > I tried to plot a 'ramp function' as follows (sympy 0.7.2 on OSX):
> >
> > from sympy import *
> > x = Symbol('x',real = True)
> > f = Lambda(x, Max(x,5))
> > plot(f(x), (x,0,10))
> >
> > but I get the exception shown below on the last line. Should I be doing
> this
> > differently ?
> > When evaluating the function f at some values, it looks like it is
> returning
> > the correct values.
> >
> > best regards,
> >
> > Andre
> >
> > stack trace:
> >
> > Traceback (most recent call last):
> >   File "/tmp/test.py", line 6, in <module>
> >     plot(f(x), (x,0,10))
> >   File
> >
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sympy/plotting/plot.py",
>
> > line 1165, in plot
> >     plots.show()
> >   File
> >
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sympy/plotting/plot.py",
>
> > line 193, in show
> >     self._backend.show()
> >   File
> >
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sympy/plotting/plot.py",
>
> > line 946, in show
> >     self.process_series()
> >   File
> >
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sympy/plotting/plot.py",
>
> > line 838, in process_series
> >     collection = LineCollection(s.get_segments())
> >   File
> >
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sympy/plotting/plot.py",
>
> > line 461, in get_segments
> >     f_start = f(self.start)
> >   File
> >
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/sympy/plotting/experimental_lambdify.py",
>
> > line 204, in __call__
> >     result = self.lambda_func(args)
> >   File "<string>", line 1, in <lambda>
> > TypeError: no ordering relation is defined for complex numbers
> >
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