matplotlibで画像が表示されない

シグモイド関数をグラフに描画しようとした時にmatplotlib.pylabをpltとして取り込みました。plt.plot(x, y)までは上手くいっていると思うのですが、plt.show()でRunTimeErrorが起こり画像が表示されません。どなたか原因を教えていただけませんか
どうかよろしくお願いします

以下、実際のコードです

def sigmoid(x):
    return 1 / (1 + np.exp(-x))

import numpy as np
import matplotlib.pylab as plt

x = np.arange(-5.0, 5.0, 0.1)
y = sigmoid(x)

plt.plot(x, y)
plt.show()


以下、エラーメッセージです


---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
/anaconda/lib/python3.6/site-packages/IPython/core/formatters.py in __call__(self, obj)
    305                 pass
    306             else:
--> 307                 return printer(obj)
    308             # Finally look for special method names
    309             method = get_real_method(obj, self.print_method)

/anaconda/lib/python3.6/site-packages/IPython/core/pylabtools.py in <lambda>(fig)
    225 
    226     if 'png' in formats:
--> 227         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
    228     if 'retina' in formats or 'png2x' in formats:
    229         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

/anaconda/lib/python3.6/site-packages/IPython/core/pylabtools.py in print_figure(fig, fmt, bbox_inches, **kwargs)
    117 
    118     bytes_io = BytesIO()
--> 119     fig.canvas.print_figure(bytes_io, **kw)
    120     data = bytes_io.getvalue()
    121     if fmt == 'svg':

/anaconda/lib/python3.6/site-packages/matplotlib/backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, **kwargs)
   2190                     orientation=orientation,
   2191                     dryrun=True,
-> 2192                     **kwargs)
   2193                 renderer = self.figure._cachedRenderer
   2194                 bbox_inches = self.figure.get_tightbbox(renderer)

/anaconda/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py in print_png(self, filename_or_obj, *args, **kwargs)
    543 
    544     def print_png(self, filename_or_obj, *args, **kwargs):
--> 545         FigureCanvasAgg.draw(self)
    546         renderer = self.get_renderer()
    547         original_dpi = renderer.dpi

/anaconda/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py in draw(self)
    462 
    463         try:
--> 464             self.figure.draw(self.renderer)
    465         finally:
    466             RendererAgg.lock.release()

/anaconda/lib/python3.6/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     61     def draw_wrapper(artist, renderer, *args, **kwargs):
     62         before(artist, renderer)
---> 63         draw(artist, renderer, *args, **kwargs)
     64         after(artist, renderer)
     65 

/anaconda/lib/python3.6/site-packages/matplotlib/figure.py in draw(self, renderer)
   1141 
   1142             mimage._draw_list_compositing_images(
-> 1143                 renderer, self, dsu, self.suppressComposite)
   1144 
   1145             renderer.close_group('figure')

/anaconda/lib/python3.6/site-packages/matplotlib/image.py in _draw_list_compositing_images(renderer, parent, dsu, suppress_composite)
    137     if not_composite or not has_images:
    138         for zorder, a in dsu:
--> 139             a.draw(renderer)
    140     else:
    141         # Composite any adjacent images together

/anaconda/lib/python3.6/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     61     def draw_wrapper(artist, renderer, *args, **kwargs):
     62         before(artist, renderer)
---> 63         draw(artist, renderer, *args, **kwargs)
     64         after(artist, renderer)
     65 

/anaconda/lib/python3.6/site-packages/matplotlib/axes/_base.py in draw(self, renderer, inframe)
   2407             renderer.stop_rasterizing()
   2408 
-> 2409         mimage._draw_list_compositing_images(renderer, self, dsu)
   2410 
   2411         renderer.close_group('axes')

/anaconda/lib/python3.6/site-packages/matplotlib/image.py in _draw_list_compositing_images(renderer, parent, dsu, suppress_composite)
    137     if not_composite or not has_images:
    138         for zorder, a in dsu:
--> 139             a.draw(renderer)
    140     else:
    141         # Composite any adjacent images together

/anaconda/lib/python3.6/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     61     def draw_wrapper(artist, renderer, *args, **kwargs):
     62         before(artist, renderer)
---> 63         draw(artist, renderer, *args, **kwargs)
     64         after(artist, renderer)
     65 

/anaconda/lib/python3.6/site-packages/matplotlib/axis.py in draw(self, renderer, *args, **kwargs)
   1136         ticks_to_draw = self._update_ticks(renderer)
   1137         ticklabelBoxes, ticklabelBoxes2 = self._get_tick_bboxes(ticks_to_draw,
-> 1138                                                                 renderer)
   1139 
   1140         for tick in ticks_to_draw:

/anaconda/lib/python3.6/site-packages/matplotlib/axis.py in _get_tick_bboxes(self, ticks, renderer)
   1076         for tick in ticks:
   1077             if tick.label1On and tick.label1.get_visible():
-> 1078                 extent = tick.label1.get_window_extent(renderer)
   1079                 ticklabelBoxes.append(extent)
   1080             if tick.label2On and tick.label2.get_visible():

/anaconda/lib/python3.6/site-packages/matplotlib/text.py in get_window_extent(self, renderer, dpi)
    965             raise RuntimeError('Cannot get window extent w/o renderer')
    966 
--> 967         bbox, info, descent = self._get_layout(self._renderer)
    968         x, y = self.get_unitless_position()
    969         x, y = self.get_transform().transform_point((x, y))

/anaconda/lib/python3.6/site-packages/matplotlib/text.py in _get_layout(self, renderer)
    351         tmp, lp_h, lp_bl = renderer.get_text_width_height_descent('lp',
    352                                                          self._fontproperties,
--> 353                                                          ismath=False)
    354         offsety = (lp_h - lp_bl) * self._linespacing
    355 

/anaconda/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py in get_text_width_height_descent(self, s, prop, ismath)
    237 
    238         flags = get_hinting_flag()
--> 239         font = self._get_agg_font(prop)
    240         font.set_text(s, 0.0, flags=flags)  # the width and height of unrotated string
    241         w, h = font.get_width_height()

/anaconda/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py in _get_agg_font(self, prop)
    277         font = get_font(
    278             fname,
--> 279             hinting_factor=rcParams['text.hinting_factor'])
    280 
    281         font.clear()

RuntimeError: In FT2Font: Can not load face.

<matplotlib.figure.Figure at 0x1116a7128>