matplotlib-users

[Matplotlib-users] errorbar and legend

[Humufr <hu...@ya...>]

		Hello,

I did probably something not good but it seems for me that the legend() 
function is not working properly (at least with errorbar)

x = arange(0,1.0,0.01)
p1 = errorbar(x,x,x,fmt='o') # or errorbar(x,x,x,fmt='o')
legend()

it seems to put in the legend all the points and lines.

I tried to do a

legend((p1),('p1'))

but it's not working, you have to do:

legend((p1,),('p1',))

to obtain the legend. Perhaps that must be indicate in the documentation 
that a you need a tuple and the method to have a legend with errorbar.


Thanks,

N.

[Matplotlib-users] Surface plot queries

[Neil P. <mat...@ke...>]

Hi,

I've been giving matplotlib (0.85) a spin, as a front end for 
'exploring' scientific simulation results. Now I've got the data in and 
had a play, there's been a few things which have confused me somewhat 
about the API/features:

* One of the most obvious obstacles at the moment is that I'm plotting 
surface plots, using contour[f] primarily, and haven't found an obvious 
way of removing 'previous' results from axes. Should this work with 
'gca().hold(False)' or equivalent? It doesn't seem to. As such I'm 
currently deleting and recreating the axes each time I change the data. 
  While this is not great, it is faster than not doing so, since 
otherwise the graph accumulates contours and increasingly takes long to 
redraw. I suppose I'm asking whether there is the equivalent of 
[axes].set_ydata(), but for contours :)

* Previously I've been using gnuplot to create pngs, which I can then 
form into a time series, mostly just plotting the data as a 'matrix'. 
While I take it for granted that python/matplotlib are loading/plotting 
the data in 'real-time' compared to just flicking between 
gnuplot-generated png's, pcolor is rather slow for me, and I'm unsure 
exactly what the other approaches (eg. imshow?) are targeted towards, or 
when they are appropriate compared to pcolor. However, not only is 
pcolor slow, but for some reason it defaults to automatically selecting 
a different (overly large) automatic axis-range than contour[f].

* For some reason my install leaves me with pylab windows which have no 
proper icons in the bottom button bar. I've set MATPLOTLIBDATA and 
PYTHONPATH, since I installed the modules into a subdir of my home 
directory.

* Closing the pylab windows using the window-manager results in the 
python process continuing - should this be calling some function to 
interrupt the show() function? (I'm running GTK/GTKAgg if its relevant)

Nevertheless, given these annoyances, I'm quite happy with the results 
so far - it is perhaps already simpler than the system I had been using 
previously, and has taken very little time to get to grips with :)
Having said that, I'm not entirely clear whether pylab is intended to be 
'the' interface to matplotlib, or just a simplified front-end - it seems 
quite confusing from reading some of the online documents.

Thanks for matplotlib, (I'll think of other things to ask, in time!)

Re: [Matplotlib-users] Surface plot queries

[Ken M. <mc...@ii...>]

On Dec 8, 2005, at 6:55 PM, Neil Pilgrim wrote:
> * One of the most obvious obstacles at the moment is that I'm  
> plotting surface plots, using contour[f] primarily, and haven't  
> found an obvious way of removing 'previous' results from axes.

Axes objects have a cla() method which clears their contents.  In  
pylab, I believe the function cla() clears the current axes.

> * Previously I've been using gnuplot to create pngs, which I can  
> then form into a time series, mostly just plotting the data as a  
> 'matrix'. While I take it for granted that python/matplotlib are  
> loading/plotting the data in 'real-time' compared to just flicking  
> between gnuplot-generated png's, pcolor is rather slow for me, and  
> I'm unsure exactly what the other approaches (eg. imshow?) are  
> targeted towards, or when they are appropriate compared to pcolor.

pcolor() does a lot of work under the hood to plot things the way it  
does.  imshow() gives you a pseudocolor plot that treats the elements  
of the matrix as luminescence, which may be exactly what you want.   
Check out the "pcolor_demo.py" example (which actually uses imshow()!):

	http://matplotlib.sourceforge.net/screenshots/pcolor_demo.py

> However, not only is pcolor slow, but for some reason it defaults  
> to automatically selecting a different (overly large) automatic  
> axis-range than contour[f].

It's my understanding that this behavior is by design: pcolor()  
treats each element Z[i,j] as being in between in between the  
corresponding X and Y elements (e.g. between X[i,j] and X[i+1,j]).   
I'm far from certain about this, so please take my answer with a  
grain of salt.

> * Closing the pylab windows using the window-manager results in the  
> python process continuing - should this be calling some function to  
> interrupt the show() function? (I'm running GTK/GTKAgg if its  
> relevant)

I'm a bit confused as to what behavior you are seeing.  Does show()  
return so your script can resume executing when you close the pylab  
window, or does it never block in the first place?

> Having said that, I'm not entirely clear whether pylab is intended  
> to be 'the' interface to matplotlib, or just a simplified front-end  
> - it seems quite confusing from reading some of the online documents.

iPython+pylab appears to be "the" interface to matplotlib for Matlab- 
style interactive plotting.  Pylab on its own is pretty good for  
quick 'n dirty plotting from scripts (e.g. visualizing the results of  
some algorithm as you debug and refine it).

Matplotlib also has an object-oriented API that is much better to use  
when you are embedding matplotlib plots in other python  
applications.  The OO API is "the" interface to matplotlib in that it  
*is* matplotlib... pylab is a wrapper that manages a lot of details  
to make things more convenient.

Ken

Re: [Matplotlib-users] Surface plot queries

[John H. <jdh...@ac...>]

>>>>> "Ken" == Ken McIvor <mc...@ii...> writes:

    Ken> The OO API is "the" interface to matplotlib in that it *is*
    Ken> matplotlib... 

If matplotlib had a QOTW .... :-)

JDH

[Matplotlib-users] mathtext in labels

[Steve S. <el...@gm...>]

Hi

I have a problem when joining 2 strings in a label:

	plot(..., label = r'$x^2$')

works, but

	plot(..., label = r'$x^2 = $' + str(3))

produces labels like $x^2 = $3

I think this is because I try to join a "normal" string and a "raw" 
string. Is there a way to do this properly?

cheers,
steve

-- 
Should array indices start at 0 or 1? My compromise of 0.5 was rejected 
without, I thought, proper consideration.
-- Stan Kelly-Bootle

[Matplotlib-users] Re: mathtext in labels

[Jouni K S. <jk...@ik...>]

Steve Schmerler <el...@gm...> writes:

> 	plot(..., label = r'$x^2 = $' + str(3))
>
> produces labels like $x^2 = $3
>
> I think this is because I try to join a "normal" string and a "raw"
> string. Is there a way to do this properly?

The raw-ness is not relevant to the problem; the only thing it does it
prevent special interpretation of backslashes. What is "raw" is the
string literal in your file, not the string value.

You need to keep the dollar signs at the beginning and end. What you
want is the percent-sign operator:

  label = r'$x^2 = %d$' % 3

-- 
Jouni