plot of Piecewise function not working

[bonc...@udel.edu]

Plotting a Piecewise function fails.  I've pasted the markdown from my ipython notebook:

```python

from sympy import *

init_session()

```

    IPython console for SymPy 1.0 (Python 3.6.0-64-bit) (ground types: python)

    

    These commands were executed:

    >>> from __future__ import division

    >>> from sympy import *

    >>> x, y, z, t = symbols('x y z t')

    >>> k, m, n = symbols('k m n', integer=True)

    >>> f, g, h = symbols('f g h', cls=Function)

    >>> init_printing()

    

    Documentation can be found at http://docs.sympy.org/1.0/

```python

f = Piecewise((0,x<0), (1,x<1), (0,True))

print(f.subs(x,-0.5), f.subs(x,0.5), f.subs(x,1.5))

plot(f,(x,-1,2))

```

    0 1 0

    ---------------------------------------------------------------------------

    TypeError                                 Traceback (most recent call last)

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/experimental_lambdify.py in __call__(self, args)

        193             #The result can be sympy.Float. Hence wrap it with complex type.

    --> 194             result = complex(self.lambda_func(args))

        195             if abs(result.imag) > 1e-7 * abs(result):

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/experimental_lambdify.py in __call__(self, *args, **kwargs)

        310     def __call__(self, *args, **kwargs):

    --> 311         return self.lambda_func(*args, **kwargs)

        312 

    <string> in <lambda>(x0)

    TypeError: '<' not supported between instances of 'complex' and 'int'

    

    During handling of the above exception, another exception occurred:

    TypeError                                 Traceback (most recent call last)

    <ipython-input-2-447f720245d0> in <module>()

          1 f = Piecewise((0,x<0), (1,x<1), (0,True))

          2 print(f.subs(x,-0.5), f.subs(x,0.5), f.subs(x,1.5))

    ----> 3 plot(f,(x,-1,2))

    

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/plot.py in plot(*args, **kwargs)

       1282     plots = Plot(*series, **kwargs)

       1283     if show:

    -> 1284         plots.show()

       1285     return plots

       1286 

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/plot.py in show(self)

        183             self._backend.close()

        184         self._backend = self.backend(self)

    --> 185         self._backend.show()

        186 

        187     def save(self, path):

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/plot.py in show(self)

       1016 

       1017     def show(self):

    -> 1018         self.process_series()

       1019         #TODO after fixing https://github.com/ipython/ipython/issues/1255

       1020         # you can uncomment the next line and remove the pyplot.show() call

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/plot.py in process_series(self)

        895             # Create the collections

        896             if s.is_2Dline:

    --> 897                 collection = self.LineCollection(s.get_segments())

        898                 self.ax.add_collection(collection)

        899             elif s.is_contour:

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/plot.py in get_segments(self)

        501                     list_segments.append([p, q])

        502 

    --> 503             f_start = f(self.start)

        504             f_end = f(self.end)

        505             sample([self.start, f_start], [self.end, f_end], 0)

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/experimental_lambdify.py in __call__(self, args)

        227                                                     use_evalf=True,

        228                                                     complex_wrap_evalf=True)

    --> 229                 result = self.lambda_func(args)

        230                 warnings.warn('The evaluation of the expression is'

        231                         ' problematic. We are trying a failback method'

    /Users/boncelet/anaconda/lib/python3.6/site-packages/sympy/plotting/experimental_lambdify.py in __call__(self, *args, **kwargs)

        309 

        310     def __call__(self, *args, **kwargs):

    --> 311         return self.lambda_func(*args, **kwargs)

        312 

        313 

    <string> in <lambda>(x0)

    TypeError: '<' not supported between instances of 'complex' and 'int'

```python

```

[Z Cart.]

Hello, were you ever able to get this to work? I am having the same problem with plotting a piecewise function!

[Jia Guo]

plot(f,(x,-1,2),adaptive=False, num_of_points=200)
 

this should work

[Leonid Kovalev]

The code in the original message works as is in the current development version of SymPy (which can be obtained by cloning from GitHub.) The issue was fixed by https://github.com/sympy/sympy/pull/13826 

On Friday, March 17, 2017 at 4:20:07 PM UTC-4, bonc...@udel.edu wrote: