Cannot plot with a list of colors

[creuzige]

I have been trying to plot a list of poles, each pole with an individual color also stored in a list. If I run this as a scatter plot (see code below), the plot executes normally. (Matplotlib 3.1.1)

fig = plt.figure(figsize=(3,3), dpi=300)
ax1 = fig.add_subplot(111)
ax1.scatter([1,2,3],[4,5,6],color=['red','green','blue'])
plt.show()

However, if I try the same thing with 'pole':

fig = plt.figure(figsize=(3,3), dpi=300)
ax1 = fig.add_subplot(111, projection='stereonet')
ax1.pole([1,2,3],[4,5,6],color=['red','green','blue'])
plt.show()

I get the following error message:

---

TypeError Traceback (most recent call last)
~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/colors.py in to_rgba(c, alpha)
173 try:
--> 174 rgba = _colors_full_map.cache[c, alpha]
175 except (KeyError, TypeError): # Not in cache, or unhashable.

TypeError: unhashable type: 'list'

During handling of the above exception, another exception occurred:

ValueError Traceback (most recent call last)
~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/IPython/core/formatters.py in call(self, obj)
339 pass
340 else:
--> 341 return printer(obj)
342 # Finally look for special method names
343 method = get_real_method(obj, self.print_method)

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/IPython/core/pylabtools.py in (fig)
242
243 if 'png' in formats:
--> 244 png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
245 if 'retina' in formats or 'png2x' in formats:
246 png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/IPython/core/pylabtools.py in print_figure(fig, fmt, bbox_inches, **kwargs)
126
127 bytes_io = BytesIO()
--> 128 fig.canvas.print_figure(bytes_io, **kw)
129 data = bytes_io.getvalue()
130 if fmt == 'svg':

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, bbox_inches, **kwargs)
2047 orientation=orientation,
2048 dryrun=True,
-> 2049 **kwargs)
2050 renderer = self.figure._cachedRenderer
2051 bbox_artists = kwargs.pop("bbox_extra_artists", None)

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py in print_png(self, filename_or_obj, *args, **kwargs)
508
509 """
--> 510 FigureCanvasAgg.draw(self)
511 renderer = self.get_renderer()
512

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/backends/backend_agg.py in draw(self)
400 toolbar = self.toolbar
401 try:
--> 402 self.figure.draw(self.renderer)
403 # A GUI class may be need to update a window using this draw, so
404 # don't forget to call the superclass.

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer, *args, **kwargs)
51 finally:
52 if artist.get_agg_filter() is not None:

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/figure.py in draw(self, renderer)
1647
1648 mimage._draw_list_compositing_images(
-> 1649 renderer, self, artists, self.suppressComposite)
1650
1651 renderer.close_group('figure')

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
136 if not_composite or not has_images:
137 for a in artists:
--> 138 a.draw(renderer)
139 else:
140 # Composite any adjacent images together

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer, *args, **kwargs)
51 finally:
52 if artist.get_agg_filter() is not None:

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/axes/_base.py in draw(self, renderer, inframe)
2626 renderer.stop_rasterizing()
2627
-> 2628 mimage._draw_list_compositing_images(renderer, self, artists)
2629
2630 renderer.close_group('axes')

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
136 if not_composite or not has_images:
137 for a in artists:
--> 138 a.draw(renderer)
139 else:
140 # Composite any adjacent images together

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer, *args, **kwargs)
51 finally:
52 if artist.get_agg_filter() is not None:

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/lines.py in draw(self, renderer)
779
780 ec_rgba = mcolors.to_rgba(
--> 781 self.get_markeredgecolor(), self._alpha)
782 fc_rgba = mcolors.to_rgba(
783 self._get_markerfacecolor(), self._alpha)

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/colors.py in to_rgba(c, alpha)
174 rgba = _colors_full_map.cache[c, alpha]
175 except (KeyError, TypeError): # Not in cache, or unhashable.
--> 176 rgba = _to_rgba_no_colorcycle(c, alpha)
177 try:
178 _colors_full_map.cache[c, alpha] = rgba

~/anaconda2/envs/SNS-Analysis-py36/lib/python3.6/site-packages/matplotlib/colors.py in _to_rgba_no_colorcycle(c, alpha)
225 # float)andnp.array(...).astype(float)` all convert "0.5" to 0.5.
226 # Test dimensionality to reject single floats.
--> 227 raise ValueError("Invalid RGBA argument: {!r}".format(orig_c))
228 # Return a tuple to prevent the cached value from being modified.
229 c = tuple(c.astype(float))

ValueError: Invalid RGBA argument: ['red', 'green', 'blue']

Putting things in for loop works, but for 5000+ points, it's incredibly slow. Any suggestions?

[joferkington]

For what it's worth, there's nothing specific to mplstereonet in this case. It's better to back up and get a broader picture of how matplotlib handles plotting large numbers of points with different colors.

You don't typically explicitly color each point. Instead, you color points by attribute/etc (a ScalarMappable in matplotlib terms).

If you'd like to color things by some particular variable, you'd use ax.scatter. To use scatter on a stereonet, you need to work in native coordinates. There are functions to convert strikes/dips, or plunge/bearings, or rakes to native stereonet coordinates. For example:

import numpy as np
import matplotlib.pyplot as plt
import mplstereonet
np.random.seed(1)

strikes = np.arange(0, 360, 15)
dips = 45 * np.ones(strikes.size)
magnitude = np.random.random(strikes.size)

# Convert our strikes and dips to stereonet coordinates
lons, lats = mplstereonet.pole(strikes, dips)

# Now we'll plot our data and color by magnitude
fig, ax = mplstereonet.subplots()
sm = ax.scatter(lons, lats, c=magnitude, s=50, cmap='gist_earth')

ax.grid()
plt.show()