matplotlib-users Mailing List for matplotlib

I'm plotting a small png for use on a web page and finding that the x and y 
labels are not being displayed. If I increase the size of the figure using 
figsize then  all is ok. I've tried x/yaxis.set_clip_on(False) and axes([..]) 
without success. How can I decrease the size of the actual graph so that the 
labels are displayed?

Robert

PS If it makes a difference the code I'm using is based on the coloured 
background region code supplied by John Hunter, i.e. there are 4 subplots, each 
with a Rectangle and a scatter plot overlaid on the 4 Rectangles.

Ted Drain wrote:

> Jeff,
> Great timing!  I was just reviewing some requirements from our users 
> to be able to create ground track plots of spacecraft right after 
> launch.  Your package looks like it should easily do most of the work 
> for us!
>
> One thing I do need to be able to do is to create line plots that 
> "wrap around" a map.  We generate a lot of ground tracks that use a 
> Mercator projection covering the whole globe (x=-180->180, y=-90->90) 
> and if the line goes off one edge, we need to wrap it around to the 
> other edge instead of drawing a line segment all the way across the page.


Ted:   That is a pain - I had to work around this a couple of times in 
the basemap code (when drawing coastlines and when drawing parallels and 
meridians). 

BTW:  You won't be able to define a mercator projection that goes from 
-90 to 90 (it's singular at the poles).  You'll have to stop it at 80 or 
85 degrees.

>
> I had planning on creating a front end script to pre-process the data 
> to handle this type of capability.  The only issue with this approach 
> is that it requires multiple lines be drawn (as if you're plotting 
> multiple curves) but only one of them should show up in the legend.  I 
> was wondering anyone else has need of this and if there is a better 
> way to implement this wrapping feature when doing map plots?


That would be useful for lots of people I think - I don't know of any 
better way (other than using a non-cylindrical projection, like a polar 
stereographic).


-Jeff

-- 
Jeffrey S. Whitaker         Phone  : (303)497-6313
Meteorologist               FAX    : (303)497-6449
NOAA/OAR/CDC  R/CDC1        Email  : Jef...@no...
325 Broadway                Office : Skaggs Research Cntr 1D-124
Boulder, CO, USA 80303-3328 Web    : http://tinyurl.com/5telg

What I did in the past was to use a heuristic that said something like: if 
the next point jumps more than 80% (or something like that) of the full map 
range, then do a linear interpolation to find the point at the boundary and 
add that to the line.  Then split the line and start a new curve on the 
other side.

We probably won't get to working on this until Apr-May but I'll let you 
know what we come up with.  I'll try to set up some type of general purpose 
functions and then you can decide if they have a place in the basemap module.

Ted

At 09:52 AM 2/10/2005, Chris Barker wrote:
>Ted Drain wrote:
>>Jeff,
>>One thing I do need to be able to do is to create line plots that "wrap 
>>around" a map.  We generate a lot of ground tracks that use a Mercator 
>>projection covering the whole globe (x=-180->180, y=-90->90) and if the 
>>line goes off one edge, we need to wrap it around to the other edge 
>>instead of drawing a line segment all the way across the page.
>
>Yes, this really is a pain. If you work out a good solution, please let me 
>know, or post it to the list. I'd love to have a similar feature in my 
>wxPython FloatCanvas.
>
>-Chris
>
>
>--
>Christopher Barker, Ph.D.
>Oceanographer
>
>NOAA/OR&R/HAZMAT         (206) 526-6959   voice
>7600 Sand Point Way NE   (206) 526-6329   fax
>Seattle, WA  98115       (206) 526-6317   main reception
>
>Chr...@no...

Ted Drain wrote:
> Jeff,
> One thing I do need to be able to do is to create line plots that "wrap 
> around" a map.  We generate a lot of ground tracks that use a Mercator 
> projection covering the whole globe (x=-180->180, y=-90->90) and if the 
> line goes off one edge, we need to wrap it around to the other edge 
> instead of drawing a line segment all the way across the page.

Yes, this really is a pain. If you work out a good solution, please let 
me know, or post it to the list. I'd love to have a similar feature in 
my wxPython FloatCanvas.

-Chris


-- 
Christopher Barker, Ph.D.
Oceanographer
                                     		
NOAA/OR&R/HAZMAT         (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception

Chr...@no...

Jeff,
Great timing!  I was just reviewing some requirements from our users to be 
able to create ground track plots of spacecraft right after launch.  Your 
package looks like it should easily do most of the work for us!

One thing I do need to be able to do is to create line plots that "wrap 
around" a map.  We generate a lot of ground tracks that use a Mercator 
projection covering the whole globe (x=-180->180, y=-90->90) and if the 
line goes off one edge, we need to wrap it around to the other edge instead 
of drawing a line segment all the way across the page.

I had planning on creating a front end script to pre-process the data to 
handle this type of capability.  The only issue with this approach is that 
it requires multiple lines be drawn (as if you're plotting multiple curves) 
but only one of them should show up in the legend.  I was wondering anyone 
else has need of this and if there is a better way to implement this 
wrapping feature when doing map plots?

Ted
ps: John I promise I'll get you a Qt backend this week.  We hit a few 
delays but I should be able to get you something this afternoon.  It's 
basically a refactorization of the Qt backend that's in CVS right now with 
some drawing improvements to reduce flickering.

At 05:04 AM 2/10/2005, Jeff Whitaker wrote:
>The first matplotlib toolkit has been released.
>
>Matplotlib toolkits are collections of application-specific functions that 
>extend matplotlib.
>
>This is hopefully the first of many - additional contributions are encouraged!
>
>The basemap toolkit allows matplotlib to plot regularly-space 
>latitiude/longitude grids on map projections, including drawing 
>coastlines, political boundaries, parallels and meridians.   It currently 
>supports six map projections  (cylindrical equidistant, mercator, lambert 
>conformal conic, lambert azimuthal equal area, albers equal area and 
>stereographic).
>
>It uses routines from the proj.4 library (http://proj.maptools.org) to 
>perform cartographic transformations.
>
>Documentation - http://matplotlib.sourceforge.net/toolkits.html.
>
>Screenshot - http://matplotlib.sourceforge.net/screenshots/plotmap_large.png
>
>Example Code - http://matplotlib.sourceforge.net/screenshots/plotmap.py
>
>Examples for each map projection are included in the source release 
>(available at the sf download page 
>(http://sourceforge.net/project/showfiles.php?group_id=80706&package_id=142792).
>
>Windows binaries are provided (thanks John!) - but they do not include the 
>examples.
>
>Comments/bug reports/suggestions are welcome.
>
>-Jeff
>
>--
>Jeffrey S. Whitaker         Phone : (303)497-6313
>NOAA/OAR/CDC  R/CDC1        FAX   : (303)497-6449
>325 Broadway                Web   : http://www.cdc.noaa.gov/~jsw
>Boulder, CO, USA 80305-3328 Office: Skaggs Research Cntr 1D-124
>
>
>
>-------------------------------------------------------
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John Hunter schreef:
> >>>>> "Gerrit" =3D=3D Gerrit Holl <ge...@nl...> writes:
>=20
>     Gerrit> Hi, to plot against dates, I use 'plot_date'.  to plot
>     Gerrit> bars, I use 'bar'.  How do I plot with bars against dates?
>=20
> The key point is that all date plotting is converting your dates to
> matplotlib datenums -- see num2date and date2num, and then setting the
> tick locators and formatters properly so that they do the right thing.
>=20
> To learn about tick locators and formatters see
> http://matplotlib.sf.net/matplotlib.ticker.html and in a date specific
> contect http://matplotlib.sf.net/matplotlib.dates.html .

Ah, thank you! I've worked it out now. In case anyone's curious:

code at http://topjaklont.student.utwente.nl/creaties/plothttplog.py
result at http://topjaklont.student.utwente.nl/eigenstats/bezoekers7x6.pn=
g
(updated nightly)

yours,
Gerrit.

P.S.
I've studies the .py sources at various places and saw a few places where
I though "this could be better" (for example, __future__ placed before
docstring doesn't work for docstring). I wanted to send a patch to SF but
SF's anonymous CVS is partially down so I couldn't do a cvs up. Is
Sourceforge patches page the correct place to send patches if I want to?

--=20
Weather in Lulea / Kallax, Sweden 10/02 16:20:
	-1.0=C2=B0C light snow; low drifting snow mostly cloudy wind 11.2 m/s SS=
E (34 m above NAP)
--=20
Ervaringen met het Syndroom van Asperger:
	http://topjaklont.student.utwente.nl
Socialistische Partij:
	http://www.sp.nl/

>>>>> "Bryan" == Bryan Cole <bry...@te...> writes:

    Bryan> I'm kind of surprised no-one else has requested this: how
    Bryan> about making all matplotlib objects picklable?

It has been requested before.  I remember Prabhu once asking whether
matplotlib supports this.  He uses xmgrace, and relies heavily on the
ability to dump the figure objects to file and pick up where he left
off.  Not having this feature is a show-stopper for him.

    Bryan> The ability to save a plot to disk as a python object and
    Bryan> recall it at a later date, or send a live matplotlib figure
    Bryan> over a network socket would be really useful. I often have
    Bryan> plots I need to make small changes to at a later date.

Would it suffice to send over the data and the matplotlib commands
needed to operate on it -- or perhaps to send the image buffer as a
string.  What is the use case where sending the actual figure object
is preferred?

    Bryan> Getting the pickling of all the C-objects right might be
    Bryan> tricky, I guess.

I don't think the extension code part would be too bad.  Extension
code is mainly called at draw time and thus stores little data -- eg
the image and agg backend extension modules.  There are some
exceptions to this, eg the transformation functions and axes limits
are stored in extension code.  Although the amount of data is small,
it would be tricky to get this part right, basically because of the
way lazy values work -- see
http://matplotlib.sf.net/matplotlib.transforms.html.  But this could
be worked around with a little thought.

This is not a paradigm I need or use much in my own work -- perhaps if
it existed I would use it more.  So I probably won't take the lead on
this one, but would be happy to work with and help you or someone else
who is, and provide helper methods for the extension code, etc.

JDH

>>>>> "Gerrit" == Gerrit Holl <ge...@nl...> writes:

    Gerrit> Hi, to plot against dates, I use 'plot_date'.  to plot
    Gerrit> bars, I use 'bar'.  How do I plot with bars against dates?

The key point is that all date plotting is converting your dates to
matplotlib datenums -- see num2date and date2num, and then setting the
tick locators and formatters properly so that they do the right thing.

To learn about tick locators and formatters see
http://matplotlib.sf.net/matplotlib.ticker.html and in a date specific
contect http://matplotlib.sf.net/matplotlib.dates.html .

Once you have digested that, take a look at the plot_date
implementation in axes.py.  Basically all it does is try to make an
intelligent guess about which locator and formatter to use, and then
forwards to data to "plot".

So all you have to do is make the intelligent choice about locator and
formatters yourself, and send the date2num data directly to bar.

(nice signature, btw)

JDH

Hi,

to plot against dates, I use 'plot_date'.
to plot bars, I use 'bar'.
How do I plot with bars against dates?

yours,
Gerrit Holl.

--=20
Weather in Lulea / Kallax, Sweden 10/02 14:20:
	0.0=C2=B0C low drifting snow mostly cloudy wind 11.2 m/s SSE (34 m above=
 NAP)
--=20
Ervaringen met het Syndroom van Asperger:
	http://topjaklont.student.utwente.nl
Socialistische Partij:
	http://www.sp.nl/

I'm kind of surprised no-one else has requested this: how about making all
matplotlib objects picklable?

The ability to save a plot to disk as a python object and recall it at a
later date, or send a live matplotlib figure over a network socket would
be really useful. I often have plots I need to make small changes to at a
later date.

Getting the pickling of all the C-objects right might be tricky, I guess.

Bryan

The first matplotlib toolkit has been released.

Matplotlib toolkits are collections of application-specific functions 
that extend matplotlib.

This is hopefully the first of many - additional contributions are 
encouraged!

The basemap toolkit allows matplotlib to plot regularly-space 
latitiude/longitude grids on map projections, including drawing 
coastlines, political boundaries, parallels and meridians.   It 
currently supports six map projections  (cylindrical equidistant, 
mercator, lambert conformal conic, lambert azimuthal equal area, albers 
equal area and stereographic).

It uses routines from the proj.4 library (http://proj.maptools.org) to 
perform cartographic transformations.

Documentation - http://matplotlib.sourceforge.net/toolkits.html.

Screenshot - http://matplotlib.sourceforge.net/screenshots/plotmap_large.png

Example Code - http://matplotlib.sourceforge.net/screenshots/plotmap.py

Examples for each map projection are included in the source release 
(available at the sf download page 
(http://sourceforge.net/project/showfiles.php?group_id=80706&package_id=142792).

Windows binaries are provided (thanks John!) - but they do not include 
the examples.

Comments/bug reports/suggestions are welcome.

-Jeff

-- 
Jeffrey S. Whitaker         Phone : (303)497-6313
NOAA/OAR/CDC  R/CDC1        FAX   : (303)497-6449
325 Broadway                Web   : http://www.cdc.noaa.gov/~jsw
Boulder, CO, USA 80305-3328 Office: Skaggs Research Cntr 1D-124

John Hunter wrote:
> 
> Below is a script that shows one way to do it....  
> 
> Is this what you are looking for?

Yep, although I wasn't expecting someone to write the script for me! A simple - 
check out the Rectangle command would have sufficed - which, incidentally is 
exactly what I was reading in the user manual when your email came in :-)

Much appreciated.

Robert

John Hunter wrote:
> 
> You can try this as an alternative download site --
> 
> http://amath.colorado.edu/faculty/fperez/python/pyworkshop/doc/pylab_users_guide_0.71.pdf
> 
> Hope this helps!  

It worked perfectly at the first attempt - thanks!

Robert

>>>>> "Robert" == Robert Leftwich <ro...@le...> writes:

    Robert> I have a requirement to generate a scatter plot with the
    Robert> background divided into 4 equal rectangular regions, each
    Robert> a different colour/shade indicating a particular
    Robert> characteristic of the points in that region. What is the
    Robert> best way to do this in matplotlib?

Below is a script that shows one way to do it.  If you don't like the
black border surrounding the different colored quadrants, you can set
the "edgecolor" property to be the same as the "facecolor"

Is this what you are looking for?
JDH

from pylab import *

# lower left quadrant
r1 = Rectangle( (0.0, 0.0), 5, 5, facecolor='yellow')

# lower right quadrant
r2 = Rectangle( (5.0, 0.0), 5, 5, facecolor='red')

# upper left quadrant
r3 = Rectangle( (0.0, 5.0), 5, 5, facecolor='blue')

# upper right quadrant
r4 = Rectangle( (5.0, 5.0), 5, 5, facecolor='green')

ax = subplot(111)
for r in (r1,r2,r3,r4):
    ax.add_patch(r)

scatter(10*rand(100), 10*rand(100))
axis([0, 10, 0, 10])
show()

>>>>> "Robert" == Robert Leftwich <ro...@le...> writes:

    Robert> I've tried a number of approaches on Linux and XP,
    Robert> including remote desktop into another box on the other
    Robert> side of the country, but all approaches failed. The only
    Robert> commonality between the 2 setups is we are both using
    Robert> IPCop as a firewall and are in Australia.

You can try this as an alternative download site --

http://amath.colorado.edu/faculty/fperez/python/pyworkshop/doc/pylab_users_guide_0.71.pdf

Hope this helps!  

JDH

John Hunter wrote:
> 
>     Perry> Secondly, this example asks for a threshold based on
>     Perry> prenormalized data values (i.e., image value of 30). To get
>     Perry> what the user wants, the user must either define the alpha
>     Perry> map to match the normalized value of 30 or normalize the
>     Perry> data to match 30 to the alpha map threshold. It's not so
>     Perry> obvious to me how this is best handled. A fancier
>     Perry> normalization function that uses data-based thresholds to
>     Perry> map to color map thresholds? Otherwise, it may be fairly
>     Perry> painful to apply in practice. A convenient way to define a
>     Perry> color map based on data values and how the data will be
>     Perry> normalized?
> 
> I'll think about these issues -- gotta run now.  But they are
> orthogonal to having an alpha channel in the colormap, no?
> 
Well, yes and no. Yes in that this can be implemented without 
dealing with the issue, no in that it may not be easily used by
just dealing with that. This has come up before and it makes me
think that some tool (I'm thinking about an optional argument to
normalize or something defining a correspondence between a data
value and a normalized value) is needed to address that, and
there are a number of different approaches that could be taken.
I was just wondering if you had any thoughts about the best
way to do that.

Perry 

>>>>> "Cindy" == Cindy Hodgins Burian <cho...@pr...> writes:

    Cindy> I'm having some problems compiling matplotlib 0.7.1 on
    Cindy> solaris 8.  I believe I have all the prerequisites there.
    Cindy> If I try to compile with setup.py as it is originally,
    Cindy> immediately it complains with "sh: pkg-config: not found",
    Cindy> and finally dies after working a while.  If I change
    Cindy> "BUILD_GTKAGG = 0" it compiles with some complaints like

    Cindy> /usr/local/pkg/python/include/python2.3/pyconfig.h:856:1:
    Cindy> warning: "_XOPEN_SOURCE" redefined <command line>:1:1:
    Cindy> warning: this is the location of the previous definition

I believe this is a solaris compiler bug -- we've seen it a couple of
times before.  Search the matplotlib-users mailing list archives for

_XOPEN_SOURCE

at http://sourceforge.net/mailarchive/forum.php?forum_id=33405

I can't remember the answer, but I know there are a few posts on the
subject there...

JDH

>>>>> "Perry" == Perry Greenfield <pe...@st...> writes:

    Perry> Should self._alpha_lut always copy the blue segment data
    Perry> (or are you showing what the user would have to do?) I
    Perry> would have guessed that it would default to being always 1
    Perry> (I think that's the intent above but how does one then
    Perry> define it independently outside of the class definition.

Uh, maybe I have the flu.  I meant


   self._alpha_lut  = makeMappingArray(self.N,
                     self._segmentdata.get('alpha', [1.0, 1.0]) 

I'm not sure about the [1.0, 1.0] -- that's your job :-)  

What I'm trying to say is that we can use the dict get method to
default to the current behavior if the alpha channel is not defined in
the segmentdata....

    Perry> Secondly, this example asks for a threshold based on
    Perry> prenormalized data values (i.e., image value of 30). To get
    Perry> what the user wants, the user must either define the alpha
    Perry> map to match the normalized value of 30 or normalize the
    Perry> data to match 30 to the alpha map threshold. It's not so
    Perry> obvious to me how this is best handled. A fancier
    Perry> normalization function that uses data-based thresholds to
    Perry> map to color map thresholds? Otherwise, it may be fairly
    Perry> painful to apply in practice. A convenient way to define a
    Perry> color map based on data values and how the data will be
    Perry> normalized?

I'll think about these issues -- gotta run now.  But they are
orthogonal to having an alpha channel in the colormap, no?

Cheers -- hope you're feeling better!

JDH