Make plot methods accept 'empty' input to return empty Graphics object

[chapoton]

list_plot does not accept empty lists:

list_plot([1],rgbcolor=(1,0,0))+list_plot([],rgbcolor=(0,0,1))

IndexError: list index out of range

does not work, whereas

list_plot([1],rgbcolor=(1,0,0))+list_plot([2],rgbcolor=(0,0,1))

does work. It would be nicer if list_plot of empty lists gives an empty graphics object.

Apply: trac_7570_empty_graphics.2.2.patch​

[kcrisman]

Incidentally, this is also true of things like point(), where an empty list of points yields an error (as far as I remember). We should check ALL plot methods to ensure that empty input yields Graphics() or something like that, at least for the 2-d versions. Changing summary appropriately.

[ryan]

make list_plot() and point() accept empty lists and return empty Graphics() object

[ryan]

The patch was made against sage-4.6.0

It handles empty lists as input to arrow, line, point, and plot.

I'm not sure what other plotting functions would benefit from empty lists as input.

[gagansekhon]

sage/plot/point.py fails.

When I passed an empty list I got an error.

sage: point([]) ERROR: An unexpected error occurred while tokenizing input The following traceback may be corrupted or invalid The error message is: ('EOF in multi-line statement', (273, 0))

---

ValueError? Traceback (most recent call last)

/Applications/sage4.6/devel/sage-main/<ipython console> in <module>()

/Applications/sage4.6/local/lib/python2.6/site-packages/IPython/Prompts.pyc in call(self, arg)

549 550 # and now call a possibly user-defined print mechanism

--> 551 manipulated_val = self.display(arg)

552 553 # user display hooks can change the variable to be stored in

/Applications/sage4.6/local/lib/python2.6/site-packages/IPython/Prompts.pyc in _display(self, arg)

575 return IPython.generics.result_display(arg) 576 except TryNext?:

--> 577 return self.shell.hooks.result_display(arg)

578 579 # Assign the default display method:

/Applications/sage4.6/local/lib/python2.6/site-packages/IPython/hooks.pyc in call(self, *args, kw)

139 #print "prio",prio,"cmd",cmd #dbg 140 try:

--> 141 ret = cmd(*args, kw)

142 return ret 143 except ipapi.TryNext?, exc:

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/misc/displayhook.pyc in result_display(ip_self, obj)

148 # IPython's default result_display() uses the IPython.genutils.Term.cout stream. 149 # See also local/lib/python2.6/site-packages/IPython/hooks.py.

--> 150 print_obj(IPython.genutils.Term.cout, obj)

151 152 def displayhook(obj):

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/misc/displayhook.pyc in print_obj(out_stream, obj)

140 if _check_tall_list_and_print(out_stream, obj): 141 return

--> 142 print >>out_stream, obj

143 144 def result_display(ip_self, obj):

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/structure/sage_object.so in sage.structure.sage_object.SageObject?.repr (sage/structure/sage_object.c:1341)()

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/plot/plot.pyc in _repr_(self)

1078 """ 1079 if SHOW_DEFAULT:

-> 1080 self.show()

1081 return 1082 else:

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/plot/misc.pyc in wrapper(*args, kwds)

82 kwds[self.name + "options"] = suboptions 83

---> 84 return func(*args, kwds)

85 86 from sage.misc.sageinspect import sage_getsource

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/plot/plot.pyc in show(self, kwds)

1737 if optionsfilename? is None: 1738 optionsfilename? = sage.misc.misc.tmp_filename() + '.png'

-> 1739 self.save(options)

1740 os.system('%s %s 2>/dev/null 1>/dev/null &' % \ 1741 (sage.misc.viewer.browser(), optionsfilename?))

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/plot/plot.pyc in save(self, filename, dpi, savenow, *args, kwds)

2386 options=dict() 2387 optionstransparent?=kwds.pop('transparent',False)

-> 2388 figure=self.matplotlib(*args, kwds)

2389 # You can output in PNG, PS, EPS, PDF, or SVG format, depending on the file extension. 2390 # matplotlib looks at the file extension to see what the renderer should be.

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/plot/plot.pyc in matplotlib(self, filename, xmin, xmax, ymin, ymax, figsize, figure, sub, axes, axes_labels, fontsize, frame, verify, aspect_ratio, gridlines, gridlinesstyle, vgridlinesstyle, hgridlinesstyle, show_legend, legend_options, axes_pad, ticks_integer, tick_formatter, ticks)

1954 #add all the primitives to the subplot 1955 for g in self.objects:

-> 1956 g._render_on_subplot(subplot)

1957 1958 #add the legend if requested

/Applications/sage4.6/local/lib/python2.6/site-packages/sage/plot/point.pyc in _render_on_subplot(self, subplot)

271 scatteroptions={} 272 if not faceted: scatteroptionsedgecolors? = 'none'

--> 273 subplot.scatter(self.xdata, self.ydata, s=s, c=c, alpha=a, zorder=z, label=optionslegend_label?, scatteroptions)

274 275

/Applications/sage4.6/local/lib/python2.6/site-packages/matplotlib/axes.pyc in scatter(self, x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, faceted, verts, kwargs)

5811 temp_y = y 5812

-> 5813 minx = np.amin(temp_x)

5814 maxx = np.amax(temp_x) 5815 miny = np.amin(temp_y)

/Applications/sage4.6/local/lib/python2.6/site-packages/numpy/core/fromnumeric.pyc in amin(a, axis, out)

1641 except AttributeError?: 1642 return _wrapit(a, 'min', axis, out)

-> 1643 return amin(axis, out)

1644 1645

ValueError?: zero-size array to ufunc.reduce without identity

[jason]

Thanks for working on polishing these things!

One quick comment from just glancing at the patch: there is a typo that occurs twice in the patch: "returns and empty plot" (where "and" should be "an").

[ryan]

funny...I can't reproduce this error on my local sage install. However, on a remote sage install (i.e., sage.math), I get the error. However, the error is triggered (I think) because the remote installation can't display graphics.

Try: [[[ a = point([]) type(a) ]]] a is of type sage.plot.plot.Graphics()

[ryan]

Try: a = point([]) type(a) a is of type sage.plot.plot.Graphics

[ryan]

1. fixed the typos
2. changed arrow2d a bit.

[ryan]

This latest patch now fixes the bug _actually_ described in the ticket :)

[ryan]

added documentation

[aly.deines]

The only test that didn't pass was ./sage -t devel/sage/sage/plot/arrow.py and I think it's only because you have line 412 in:

sage: arrow2d(headpoint=None, tailpoint) 

If you delete that line, the tests pass and everything looks good.

[aly.deines]

This fixes the doctest.

[kcrisman]

Positive reviewer, can you add your (real) name to the reviewer list?

[jdemeyer]

Please specify which patches have to be applied.

[kcrisman]

I hate to do this, because I *really* want this in - just yesterday had to write all sorts of dumb if/then clauses to get around this. But the commit message on the most recent patch is totally uninformative, and unfortunately I don't have time to fix that now.

[jdemeyer]

There is also a Sphinx error:

/mnt/usb1/scratch/jdemeyer/merger/sage-4.6.2.alpha3/local/lib/python2.6/site-packages/sage/plot/plot.py:docstring of sage.plot.plot:157: (ERROR/3) Unexpected indentation.

[jdemeyer]

Can somebody please fix the trivial issues with this ticket?

[kcrisman]

Use this patch only

[kcrisman]

I think this fixes both issues, as well as corrects several 'emtpy' occurrences.

[jason]

There is a problem with the code on the final merged patch: why wasn't len()==0 used as a test? The problem is illustrated here: ​http://groups.google.com/group/sage-support/browse_thread/thread/fb53b9d908acfb4

I've opened #11787 to correct this.