ValueError ("Contour levels must be increasing")

[BordeauxDave]

Greetings! I run your few line example exactly as it appears on your web sites, and it crashes as follows:

$ python testCorner0.py
Traceback (most recent call last):
File "testCorner0.py", line 6, in
figure = corner.corner(samples)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/corner.py", line 330, in corner
*_hist2d_kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/corner.py", line 519, in hist2d
ax.contour(X2, Y2, H2.T, V, *_contour_kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/init.py", line 1846, in inner
return func(ax, _args, *_kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/axes/_axes.py", line 5641, in contour
return mcontour.QuadContourSet(self, _args, *_kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/contour.py", line 1448, in init
ContourSet.init(self, ax, _args, *_kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/contour.py", line 874, in init
self._process_args(_args, *_kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/contour.py", line 1469, in _process_args
x, y, z = self._contour_args(args, kwargs)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/contour.py", line 1564, in _contour_args
self._contour_level_args(z, args)
File "/work/myPython/epd_free-7.3-1-rh5-x86/lib/python2.7/site-packages/matplotlib-1.5.0_511.gf420992-py2.7-linux-i686.egg/matplotlib/contour.py", line 1200, in _contour_level_args
raise ValueError("Contour levels must be increasing")
ValueError: Contour levels must be increasing

My OS, below. Thanks, and regards to all, David.

$ lsb_release -a
LSB Version: :core-3.1-ia32:core-3.1-noarch:graphics-3.1-ia32:graphics-3.1-noarch
Distributor ID: ScientificSL
Description: Scientific Linux SL release 5.5 (Boron)
Release: 5.5
Codename: Boron

[kbarbary]

Assuming you're running the example block under "Usage" in the README.rst, I can't reproduce this error. I'm on Ubuntu, using conda, python 2.7.11, numpy=1.10.2, matplotlib=1.5.0.

[BordeauxDave]

Le 06/01/2016 20:04, Kyle Barbary a écrit :

Assuming you're running the example block under "Usage" in the
README.rst, I can't reproduce this error. I'm on Ubuntu, using conda,
python 2.7.11, numpy=1.10.2, matplotlib=1.5.0.

Well, thank you for trying. I am indeed doing:

import numpy as np
import corner

ndim, nsamples = 5, 10000
samples = np.random.randn(ndim * nsamples).reshape([nsamples, ndim])
figure = corner.corner(samples)
figure.savefig("corner.png")

to which I add that

corner.version
u'1.0.0'

np.version
'1.10.1'
Any other suggestions are welcome, David.

[BordeauxDave]

Progress! Two things...

1. I execute to completion without errors, but with contour-less plots, by changing the line to
   corner.corner(samples, plot_contours=False)

2. Towards the end of corner.py, the contours array V is created:
   V = np.empty(len(levels))
   for i, v0 in enumerate(levels):
   try:
   V[i] = Hflat[sm <= v0][-1]
   except:
   V[i] = Hflat[0]

A print of "levels" shows that it is ascending. But V is descending!
I added a few lines:
print (" das corner VVVVV: ", V)
V = V[::-1]
print (" das corner VVVVV: ", V)
and here is a sample of what goes to my screen:
das corner VVVVV: [ 196. 140. 71. 29.]
das corner VVVVV: [ 29. 71. 140. 196.]

With this reverse of V,
corner.corner(samples, plot_contours=True)
now works nicely.

I will leave it to you experts to understand why V is okay on some systems but not on mine!
Thank you for listening, David.

[dfm]

This error was added in matplotlib 1.5.1 because of a bug in all versions of contourf prior to 1.5.0. See #65 for the relevant issue. It's not quite as simple as just sorting the levels.

[dfm]

This should be fixed in version 1.0.1 (see #70). Give it a shot.

[BordeauxDave]

Yes! my problem is indeed resolved. Thanks again to all, David.