Error at step 14, when plotting the compressed spectrogram

[ianni67]

Hi Tim! vert useful and interesting job. Unfortunately I got an error. I cloned the git, ran the example and, after step 13, i.e., after:

mel_spec = make_mel(wav_spectrogram, mel_filter, shorten_factor = shorten_factor)

got the following warning:

/usr/local/lib/python2.7/dist-packages/scipy/ndimage/interpolation.py:600: UserWarning: From scipy 0.13.0, the output shape of zoom() is calculated with round() instead of int() - for these inputs the size of the returned array has changed.
  "the returned array has changed.", UserWarning)

then at the following step 14, i.e. after:

# plot the compressed spec
fig, ax = plt.subplots(nrows=1,ncols=1, figsize=(20,4))

cax = ax.matshow(mel_spec, interpolation='nearest', aspect='auto', cmap=plt.cm.afmhot, origin='lower')
fig.colorbar(cax)
plt.title('mel Spectrogram')

I got the following error message:

ValueError                                Traceback (most recent call last)
/usr/local/lib/python2.7/dist-packages/IPython/core/formatters.pyc 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)

/usr/local/lib/python2.7/dist-packages/IPython/core/pylabtools.pyc in <lambda>(fig)
    238 
    239     if 'png' in formats:
--> 240         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
    241     if 'retina' in formats or 'png2x' in formats:
    242         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

/usr/local/lib/python2.7/dist-packages/IPython/core/pylabtools.pyc in print_figure(fig, fmt, bbox_inches, **kwargs)
    122 
    123     bytes_io = BytesIO()
--> 124     fig.canvas.print_figure(bytes_io, **kw)
    125     data = bytes_io.getvalue()
    126     if fmt == 'svg':

/usr/local/lib/python2.7/dist-packages/matplotlib/backend_bases.pyc in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, **kwargs)
   2198                     orientation=orientation,
   2199                     dryrun=True,
-> 2200                     **kwargs)
   2201                 renderer = self.figure._cachedRenderer
   2202                 bbox_inches = self.figure.get_tightbbox(renderer)

/usr/local/lib/python2.7/dist-packages/matplotlib/backends/backend_agg.pyc 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

/usr/local/lib/python2.7/dist-packages/matplotlib/backends/backend_agg.pyc in draw(self)
    462 
    463         try:
--> 464             self.figure.draw(self.renderer)
    465         finally:
    466             RendererAgg.lock.release()

/usr/local/lib/python2.7/dist-packages/matplotlib/artist.pyc 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 

/usr/local/lib/python2.7/dist-packages/matplotlib/figure.pyc in draw(self, renderer)
   1142 
   1143             mimage._draw_list_compositing_images(
-> 1144                 renderer, self, dsu, self.suppressComposite)
   1145 
   1146             renderer.close_group('figure')

/usr/local/lib/python2.7/dist-packages/matplotlib/image.pyc 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

/usr/local/lib/python2.7/dist-packages/matplotlib/artist.pyc 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 

/usr/local/lib/python2.7/dist-packages/matplotlib/axes/_base.pyc in draw(self, renderer, inframe)
   2424             renderer.stop_rasterizing()
   2425 
-> 2426         mimage._draw_list_compositing_images(renderer, self, dsu)
   2427 
   2428         renderer.close_group('axes')

/usr/local/lib/python2.7/dist-packages/matplotlib/image.pyc 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

/usr/local/lib/python2.7/dist-packages/matplotlib/artist.pyc 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 

/usr/local/lib/python2.7/dist-packages/matplotlib/image.pyc in draw(self, renderer, *args, **kwargs)
    541         else:
    542             im, l, b, trans = self.make_image(
--> 543                 renderer, renderer.get_image_magnification())
    544             if im is not None:
    545                 renderer.draw_image(gc, l, b, im)

/usr/local/lib/python2.7/dist-packages/matplotlib/image.pyc in make_image(self, renderer, magnification, unsampled)
    768         return self._make_image(
    769             self._A, bbox, transformed_bbox, self.axes.bbox, magnification,
--> 770             unsampled=unsampled)
    771 
    772     def _check_unsampled_image(self, renderer):

/usr/local/lib/python2.7/dist-packages/matplotlib/image.pyc in _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification, unsampled, round_to_pixel_border)
    424                 A, output, t, _interpd_[self.get_interpolation()],
    425                 self.get_resample(), alpha,
--> 426                 self.get_filternorm() or 0.0, self.get_filterrad() or 0.0)
    427 
    428             if created_rgba_mask:

ValueError: 3-dimensional arrays must be of dtype unsigned byte, unsigned short, float32 or float64

Would you, please, advice on how to solve this problem? Thank you very much for your help