matplotlib-users Mailing List for matplotlib

> 
>   Can you get us a gdb backtrace?
> 
> Type "gdb python" at the prompt, then at the gdb prompt, type "r 
> /usr/bin/ipython -pylab".  After it segfaults, type "bt" to get a 
> backtrace, and send the output to this list.
> 
> Mike
> 
> On 10/01/2010 07:04 AM, Eric Emsellem wrote:
> > Hi
> >
> > I just upgraded to opensuse 11.3.
> >
> > And I get now:
> >
> > ipython -pylab:
> >
> > matplotlib version 1.0.0
> > verbose.level helpful
> > platform is  linux2
> > *Segmentation fault*
> >
> >
> > Any clue?
> >
> > I am using IPython 0.10, Python 2.6.5
> >
> > Eric
> >
> >
> > 


Hello,
here is one:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00007ffff0911651 in init_path () from
/usr/lib64/python2.6/site-packages/matplotlib/_path.so
#2  0x00007ffff7b352c6 in _PyImport_LoadDynamicModule () from
/usr/lib64/libpython2.6.so.1.0
#3  0x00007ffff7b344e1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#4  0x00007ffff7b3475a in ?? () from /usr/lib64/libpython2.6.so.1.0
#5  0x00007ffff7b34bf1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#6  0x00007ffff7b351d4 in PyImport_ImportModuleLevel () from
/usr/lib64/libpython2.6.so.1.0
#7  0x00007ffff7b1f81b in ?? () from /usr/lib64/libpython2.6.so.1.0
#8  0x00007ffff7ae7cb2 in PyObject_Call () from /usr/lib64/libpython2.6.so.1.0
#9  0x00007ffff7b1fd26 in PyEval_CallObjectWithKeywords () from
/usr/lib64/libpython2.6.so.1.0
#10 0x00007ffff7b21b1e in PyEval_EvalFrameEx () from /usr/lib64
/libpython2.6.so.1.0
#11 0x00007ffff7b26431 in PyEval_EvalCodeEx () from /usr/lib64
/libpython2.6.so.1.0
#12 0x00007ffff7b1fa22 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#13 0x00007ffff7b33145 in PyImport_ExecCodeModuleEx () from
/usr/lib64/libpython2.6.so.1.0
#14 0x00007ffff7b33384 in ?? () from /usr/lib64/libpython2.6.so.1.0
#15 0x00007ffff7b344e1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#16 0x00007ffff7b3475a in ?? () from /usr/lib64/libpython2.6.so.1.0
#17 0x00007ffff7b34b35 in ?? () from /usr/lib64/libpython2.6.so.1.0
#18 0x00007ffff7b351d4 in PyImport_ImportModuleLevel () from
/usr/lib64/libpython2.6.so.1.0
#19 0x00007ffff7b1f81b in ?? () from /usr/lib64/libpython2.6.so.1.0
#20 0x00007ffff7ae7cb2 in PyObject_Call () from /usr/lib64/libpython2.6.so.1.0
#21 0x00007ffff7b1fd26 in PyEval_CallObjectWithKeywords () from
/usr/lib64/libpython2.6.so.1.0
#22 0x00007ffff7b21b1e in PyEval_EvalFrameEx () from /usr/lib64
/libpython2.6.so.1.0
#23 0x00007ffff7b26431 in PyEval_EvalCodeEx () from /usr/lib64
/libpython2.6.so.1.0
#24 0x00007ffff7b1fa22 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#25 0x00007ffff7b33145 in PyImport_ExecCodeModuleEx () from
/usr/lib64/libpython2.6.so.1.0
#26 0x00007ffff7b33384 in ?? () from /usr/lib64/libpython2.6.so.1.0
#27 0x00007ffff7b344e1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#28 0x00007ffff7b33c4b in ?? () from /usr/lib64/libpython2.6.so.1.0
#29 0x00007ffff7b34c5a in ?? () from /usr/lib64/libpython2.6.so.1.0
#30 0x00007ffff7b351d4 in PyImport_ImportModuleLevel () from
/usr/lib64/libpython2.6.so.1.0
#31 0x00007ffff7b1f81b in ?? () from /usr/lib64/libpython2.6.so.1.0
#32 0x00007ffff7ae7cb2 in PyObject_Call () from /usr/lib64/libpython2.6.so.1.0
#33 0x00007ffff7b1fd26 in PyEval_CallObjectWithKeywords () from
/usr/lib64/libpython2.6.so.1.0
#34 0x00007ffff7b21b1e in PyEval_EvalFrameEx () from /usr/lib64
/libpython2.6.so.1.0
#35 0x00007ffff7b26431 in PyEval_EvalCodeEx () from /usr/lib64
/libpython2.6.so.1.0
#36 0x00007ffff7b1fa22 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#37 0x00007ffff7b33145 in PyImport_ExecCodeModuleEx () from
/usr/lib64/libpython2.6.so.1.0
#38 0x00007ffff7b33384 in ?? () from /usr/lib64/libpython2.6.so.1.0
#39 0x00007ffff7b344e1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#40 0x00007ffff7b33c4b in ?? () from /usr/lib64/libpython2.6.so.1.0
#41 0x00007ffff7b34c5a in ?? () from /usr/lib64/libpython2.6.so.1.0
#42 0x00007ffff7b351d4 in PyImport_ImportModuleLevel () from
/usr/lib64/libpython2.6.so.1.0
#43 0x00007ffff7b1f81b in ?? () from /usr/lib64/libpython2.6.so.1.0
#44 0x00007ffff7ae7cb2 in PyObject_Call () from /usr/lib64/libpython2.6.so.1.0
#45 0x00007ffff7b1fd26 in PyEval_CallObjectWithKeywords () from
/usr/lib64/libpython2.6.so.1.0
#46 0x00007ffff7b21b1e in PyEval_EvalFrameEx () from /usr/lib64
/libpython2.6.so.1.0
#47 0x00007ffff7b26431 in PyEval_EvalCodeEx () from /usr/lib64
/libpython2.6.so.1.0
#48 0x00007ffff7b1fa22 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#49 0x00007ffff7b33145 in PyImport_ExecCodeModuleEx () from
/usr/lib64/libpython2.6.so.1.0
#50 0x00007ffff7b33384 in ?? () from /usr/lib64/libpython2.6.so.1.0
#51 0x00007ffff7b344e1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#52 0x00007ffff7b3475a in ?? () from /usr/lib64/libpython2.6.so.1.0
#53 0x00007ffff7b34bf1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#54 0x00007ffff7b351d4 in PyImport_ImportModuleLevel () from
/usr/lib64/libpython2.6.so.1.0
#55 0x00007ffff7b1f81b in ?? () from /usr/lib64/libpython2.6.so.1.0
#56 0x00007ffff7ae7cb2 in PyObject_Call () from /usr/lib64/libpython2.6.so.1.0
#57 0x00007ffff7b1fd26 in PyEval_CallObjectWithKeywords () from
/usr/lib64/libpython2.6.so.1.0
#58 0x00007ffff7b21b1e in PyEval_EvalFrameEx () from /usr/lib64
/libpython2.6.so.1.0
#59 0x00007ffff7b26431 in PyEval_EvalCodeEx () from /usr/lib64
/libpython2.6.so.1.0
#60 0x00007ffff7b1fa22 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#61 0x00007ffff7b33145 in PyImport_ExecCodeModuleEx () from
/usr/lib64/libpython2.6.so.1.0
#62 0x00007ffff7b33384 in ?? () from /usr/lib64/libpython2.6.so.1.0
#63 0x00007ffff7b344e1 in ?? () from /usr/lib64/libpython2.6.so.1.0
#64 0x00007ffff7b3475a in ?? () from /usr/lib64/libpython2.6.so.1.0
#65 0x00007ffff7b350c3 in ?? () from /usr/lib64/libpython2.6.so.1.0
#66 0x00007ffff7b351d4 in PyImport_ImportModuleLevel () from
/usr/lib64/libpython2.6.so.1.0
#67 0x00007ffff7b1f81b in ?? () from /usr/lib64/libpython2.6.so.1.0
#68 0x00007ffff7ae7cb2 in PyObject_Call () from /usr/lib64/libpython2.6.so.1.0
#69 0x00007ffff7b1fd26 in PyEval_CallObjectWithKeywords () from
/usr/lib64/libpython2.6.so.1.0
#70 0x00007ffff7b21b1e in PyEval_EvalFrameEx () from /usr/lib64
/libpython2.6.so.1.0
#71 0x00007ffff7b26431 in PyEval_EvalCodeEx () from /usr/lib64
/libpython2.6.so.1.0
#72 0x00007ffff7b1fa22 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#73 0x00007ffff7b3a791 in ?? () from /usr/lib64/libpython2.6.so.1.0
#74 0x00007ffff7ad46f0 in PyRun_InteractiveOneFlags () from
/usr/lib64/libpython2.6.so.1.0
#75 0x00007ffff7ad4811 in PyRun_InteractiveLoopFlags () from
/usr/lib64/libpython2.6.so.1.0
#76 0x00007ffff7b3b876 in PyRun_AnyFileExFlags () from
/usr/lib64/libpython2.6.so.1.0
#77 0x00007ffff7b42628 in Py_Main () from /usr/lib64/libpython2.6.so.1.0
#78 0x00007ffff6e8eb7d in __libc_start_main () from /lib64/libc.so.6
#79 0x00000000004006e9 in _start () at ../sysdeps/x86_64/elf/start.S:113
(gdb) 

openSUSE 11.3
# rpm -qa python python-matplotlib
python-matplotlib-1.0.1-17.1.x86_64
python-2.6.5-3.3.1.x86_64
# uname -a
Linux kiss 2.6.34.7-0.7-default #1 SMP 2010-12-13 11:13:53 +0100 x86_64 x86_64
x86_64 GNU/Linux

BR,
Attila

Thanks a lot Thomas,

besides that it should be

fig.colorbar(im)
instead of
ax.colorbar(im)

the example works great!

Best regards,
Daniel


2011/2/7 Eric Firing

> On 02/07/2011 10:48 AM, Daniel Mader wrote:
> > Hi,
> >
> > I am trying to add a (configurable) colorbar to a an array which I
> > simply plot with imshow().
> >
> > Could anyone please help me how to enhance it with a colorbar?
>
> Check out the gallery; several examples there use a colorbar.
> http://matplotlib.sourceforge.net/gallery.html
>
> Then look for relevant sections in the docs, such as
> http://matplotlib.sourceforge.net/users/image_tutorial.html
>
> http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.colorbar
> etc.
>
> Eric
>
> >
> > import scipy,pylab
> > import matplotlib.cm <http://matplotlib.cm> as cm # colormaps
> > import matplotlib.colors as col # colormaps
> >
> > dat = scipy.array([[1,2,3,4],[5,6,7,8]])
> >
> > fig = pylab.figure()
> > ax = pylab.gca()
> > ax.set_title('the title')
> >
> > ## here's chaos :)
> > #cmap = cm.get_cmap('rainbow', 20) # 10 discrete colors
> > #ax.imshow(dat, cmap=cmap, interpolation='nearest')
> > #fig.colorbar(dat)
> > #min,max = dat.min(),dat.max()
> >
> > ax.imshow(dat,interpolation='nearest')
> > pylab.show()
> >
> > Thanks a lot in advance,
> > Daniel
> >
>

On 02/07/2011 10:48 AM, Daniel Mader wrote:
> Hi,
>
> I am trying to add a (configurable) colorbar to a an array which I
> simply plot with imshow().
>
> Could anyone please help me how to enhance it with a colorbar?

Check out the gallery; several examples there use a colorbar. 
http://matplotlib.sourceforge.net/gallery.html

Then look for relevant sections in the docs, such as
http://matplotlib.sourceforge.net/users/image_tutorial.html
http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.colorbar
etc.

Eric

>
> import scipy,pylab
> import matplotlib.cm <http://matplotlib.cm> as cm # colormaps
> import matplotlib.colors as col # colormaps
>
> dat = scipy.array([[1,2,3,4],[5,6,7,8]])
>
> fig = pylab.figure()
> ax = pylab.gca()
> ax.set_title('the title')
>
> ## here's chaos :)
> #cmap = cm.get_cmap('rainbow', 20) # 10 discrete colors
> #ax.imshow(dat, cmap=cmap, interpolation='nearest')
> #fig.colorbar(dat)
> #min,max = dat.min(),dat.max()
>
> ax.imshow(dat,interpolation='nearest')
> pylab.show()
>
> Thanks a lot in advance,
> Daniel
>
>
>
> ------------------------------------------------------------------------------
> The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE:
> Pinpoint memory and threading errors before they happen.
> Find and fix more than 250 security defects in the development cycle.
> Locate bottlenecks in serial and parallel code that limit performance.
> http://p.sf.net/sfu/intel-dev2devfeb
>
>
>
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users

Hi,

I am trying to add a (configurable) colorbar to a an array which I simply
plot with imshow().

Could anyone please help me how to enhance it with a colorbar?

import scipy,pylab
import matplotlib.cm as cm # colormaps
import matplotlib.colors as col # colormaps

dat = scipy.array([[1,2,3,4],[5,6,7,8]])

fig = pylab.figure()
ax = pylab.gca()
ax.set_title('the title')

## here's chaos :)
#cmap = cm.get_cmap('rainbow', 20) # 10 discrete colors
#ax.imshow(dat, cmap=cmap, interpolation='nearest')
#fig.colorbar(dat)
#min,max = dat.min(),dat.max()

ax.imshow(dat,interpolation='nearest')
pylab.show()

Thanks a lot in advance,
Daniel

Jorge Scandaliaris <jorgesmbox-ml@...> writes:

< snip >
> I couldn't come up with a simple example showing the problem. My attempts so 
> far
> ended in working examples. I did find a change in my code that triggers the
> problem: My code uses a modified version of the lasso_demo example, contains 
> two
> axes, where I draw an image with imshow and a collection of circles with
> scatter. Originally scatter was called with a fixed size for all points, and I
> just changed it so each points gets a different size. 
> 
> Just don't ask me why this seemingly innocent change affects (breaks) the 
> event
> handling. I hope somebody can give me some hints. I'll keep checking the code 
> to

Because I couldn't reproduce the problem on simple examples, and also because I
have time constraints related to my work, I decided to go on ignoring this
problem (I can always avoid resizing windows...). This afternoon, I realized
that the problem had not appeared during the whole day, but then realized that
because I was debugging some changes introduced in my code, I had been using
very small images. After switching back to normal sizes, the problem came back. 

So, I modified the lasso_demo, increasing progressively the number polygons
drawn. When I reached 100000 polygons, I was able to reproduce the problem. It's
true that this a rather large number, but in my code it happens well below this
number, maybe because I assign a different color and size to each polygon. So my
previous observation that setting different sizes triggered the problem might
not be the real picture. It seems as if I was hitting some sort of limit.

Anyone would have a clue about what could be happening, or how can I try to
debug this?

Thanks,

jorges

On 02/07/2011 11:58 AM, Jouni K. Seppänen wrote:
> Jouni Seppänen <jk...@ik...> writes:
> 
>> In the meantime, I will commit a quick workaround that just disables
>> the fonts we can't handle instead of aborting with an assert.
> 
> Now committed in revision 8955 (1.0 maintenance branch) and 8956
> (svn trunk). Please test on your system.

The workaround fixes the error I was receiving.  Thank you very much!

-- 
Michael Anselmi
Class of 2011
Mathematics (B.S.)
University of Rochester
508.507.9738

On 02/07/2011 05:47 AM, Carlos Grohmann wrote:
> Hello all,
>
> I'm developing a software for Geology, using wxpython for the GUI.
> When I want to export any graphics, clicking on the
> "save" button on the MPL toolbar, I get a dialog to save the file
> (with a default "image.png" filename) and where I
> can choose between some file formats. When I select any format from
> the drop-down list, I expected it to change the extension
> of the file on the dialog, but it doesn't. So I have to set it up
> manually. Is this a bug?

Yes.  It works correctly with gtk, but it looks like there are problems 
with wx and qt4.

Eric

>
> thanks
>

On 02/07/2011 05:21 AM, Carlos Grohmann wrote:
> Hello there
>
> Is there support for exporting graphics as EMF files?
>
>> From what I've seen it seems to be discontinued.
>
> best
>
> Carlos
>
>
>

Carlos,

There is still a backend_emf.py, but I don't think it was ever complete 
(for example, it does not handle images).  It has no regular maintainer. 
  I don't know to what extent it still works.  It requires pyemf, which 
was last released in 2006.

Eric

Jouni Seppänen <jk...@ik...> writes:

>In the meantime, I will commit a quick workaround that just disables
>the fonts we can't handle instead of aborting with an assert.

Now committed in revision 8955 (1.0 maintenance branch) and 8956
(svn trunk). Please test on your system.

On 07.02.2011 17:17, Jouni K. Seppänen wrote:
> Jouni Seppänen<jk...@ik...>  writes:
>
>> I filed this in the bug tracker: https://sourceforge.net/tracker/?func=detail&aid=3175113&group_id=80706&atid=560720
>
> I installed TeX Live 2010 on my Mac in order to test this, but
> mysteriously, the pdftex.map file does not have a line for pbkdo8y. The
> closest match is
>
> pbkdo8r URWBookmanL-DemiBold ".167 SlantFont TeXBase1Encoding ReEncodeFont"<8r.enc<ubkd8a.pfb
>
> which is the same font but with another encoding. I wonder if this
> indicates a problem in the way Ubuntu sets up TeX Live?
>

Hi Jouni,

currently Ubuntu still uses Texlive 2009. I also got the same bug 
(http://article.gmane.org/gmane.comp.python.matplotlib.general/26110) 
with Texlive 2010 installed directly from tug.org.
I think it is unlikely that this is an Ubuntu specific problem, but I 
don't know for sure whether this file gets generated during the 
installation or is unmodified from the Texlive distribution.

Greetings
Alexander

Jouni Seppänen <jk...@ik...> writes:

> I filed this in the bug tracker: https://sourceforge.net/tracker/?func=detail&aid=3175113&group_id=80706&atid=560720

I installed TeX Live 2010 on my Mac in order to test this, but
mysteriously, the pdftex.map file does not have a line for pbkdo8y. The
closest match is

pbkdo8r URWBookmanL-DemiBold ".167 SlantFont TeXBase1Encoding ReEncodeFont" <8r.enc <ubkd8a.pfb

which is the same font but with another encoding. I wonder if this
indicates a problem in the way Ubuntu sets up TeX Live?

-- 
Jouni K. Seppänen
http://www.iki.fi/jks

Hello all,

I'm developing a software for Geology, using wxpython for the GUI.
When I want to export any graphics, clicking on the
"save" button on the MPL toolbar, I get a dialog to save the file
(with a default "image.png" filename) and where I
can choose between some file formats. When I select any format from
the drop-down list, I expected it to change the extension
of the file on the dialog, but it doesn't. So I have to set it up
manually. Is this a bug?

thanks

-- 
Prof. Carlos Henrique Grohmann - Geologist D.Sc.
Institute of Geosciences - Univ. of São Paulo, Brazil
http://www.igc.usp.br/pessoais/guano
http://lattes.cnpq.br/5846052449613692
Linux User #89721
________________
Can’t stop the signal.

On Feb 7, 2011, at 17:12 , Michael Anselmi wrote:

> On 02/07/2011 10:06 AM, Jouni K. Seppänen wrote:
>> Can you send me the pdftex.map file off-list?
>> 
>> Thanks for the bug report,
> 
> Certainly.  See attached.

Thanks. It looks like there is one font for which two encoding files are specified:

pbkdo8y URWBookmanL-DemiBold ".167 SlantFont TeXnANSIEncoding ReEncodeFont" <texnansi.enc <8r.enc <ubkd8a.pfb

I guess we will need to implement slightly more of a PostScript interpreter inside matplotlib to figure out which file is to be used for re-encoding the font, unless this really means some kind of a combination of the two encodings. I'll try to find out what pdftex does with this. In the meantime, I will commit a quick workaround that just disables the fonts we can't handle instead of aborting with an assert.

I filed this in the bug tracker: https://sourceforge.net/tracker/?func=detail&aid=3175113&group_id=80706&atid=560720

Jouni

Hello there

Is there support for exporting graphics as EMF files?

>From what I've seen it seems to be discontinued.

best

Carlos



-- 
Prof. Carlos Henrique Grohmann - Geologist D.Sc.
Institute of Geosciences - Univ. of São Paulo, Brazil
http://www.igc.usp.br/pessoais/guano
http://lattes.cnpq.br/5846052449613692
Linux User #89721
________________
Can’t stop the signal.

Michael Anselmi <sel...@gm...> writes:

> When trying to save a matplotlib figure as a PDF with `text.usetex =
> True' in `matplotlibrc', at some point the `PsfontsMap' function in
> `dviread.py' attempts to parse TeX Live 2010's `pdftex.map' file and
> fails.

Can you send me the pdftex.map file off-list?

Thanks for the bug report,
-- 
Jouni K. Seppänen
http://www.iki.fi/jks

Hi all,
On Sun, 6 Feb 2011 03:54:48 PM Paul Leopardi wrote:
> I'm having trouble using multiple figures with mplot3d.

I have appended an entire example script, below.

The script incrementally plots 3 curves, one in each of 3 figure windows. The 
trouble is, once Figure 2 has finished plotting, the curve for Figure 1 
disappears and is replaced by the curve for Figure 2, with the axes for Figure 
1; once Figure 3 has finished plotting, the curves for Figures 1 and 2 
disappear and are replaced by the curve for Figure 3, with the axes for Figure 
1 and Figure 2, respectively. 

The original code was written with incremental plotting because the points 
took a long time to calculate. Without incremental plotting, the figures 
stayed blank for a long time. The script below is very similar to my original 
script, but does not depend on my GluCat library.

Best, Paul
---

# -*- coding: utf-8 -*-

# Imports needed for array calculation and plotting.
from numpy import array, floor, random, empty, cos, pi
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt

# Constants to control the plotting.
C=3 # Number of curves to plot.
P=1000 # Number of points overall.
R=2 # Scaling constant to use.
N=25 # Number of points in a curve segment.
M=P/N

# Array of points.
x=empty((3,P))
rgb=empty((3))

# Plot C curves.
for i in xrange(0,C):
 # Initial point.
 x0=random.randn(3)

 # Plot a curve using a random bivector in R_{5,0}
 # with appropriate scaling.
 w=random.randn(3) * 2*pi*R/P

 # Use a new figure for each curve.
 fig=plt.figure(figsize=(15,12))
 # ax=Axes3D(fig)
 ax = fig.gca(projection='3d')
 plt.show()

 # Coordinate limits to determine the colour of the first curve segment.
 minx=array([-x0[0],x0[1],-x0[2]])
 maxx=minx.copy()

 # Split the curve into M segments, each with an appropriate colour.
 for j in range(0,M):

  # Find N points forming a curve segment by
  # exponentiating w*k for k from j*N to (j+1)*N-1.
  abot=j*N
  atop=abot+N
  for k in xrange(abot,atop):
   for h in range(0,3):
    x[h,k]=x0[h]+cos(w[h]*k)

  # Determine the colour of the curve segment.
  amid=floor((abot+atop)/2)
  for h in range(0,3):
   sign=(-1)**(h+1)
   minx[h]=min(minx[h],min(sign*x[h,abot:atop]))
   maxx[h]=max(maxx[h],max(sign*x[h,abot:atop]))
   rgb[h]=max(0.0,min((sign*x[h,amid]-minx[h])/(maxx[h]-minx[h]),1.0))

  # Plot the curve segment using the chosen colour.
  alow=(abot-1 if j>0 else abot)
  ax.plot(x[0,alow:atop],x[1,alow:atop],x[2,alow:atop],c=rgb.tolist())
  plt.draw()
 plt.show()