matplotlib-users Mailing List for matplotlib

On Tue, 2005-11-29 at 12:25 +0100, Willi Richert wrote:
> I need to draw a sequence of arrows denoting a path. There is the quiver 
> function which draws vector fields (and, btw, behaves differently from the 
> examples on the web), so this is not an option. Additionally, there is the 
> Arrow class. But it is very slow and, what's more important, draws distortet 
> arrows at some angles. Am I missing something, or are these two possibilities 
> the only options?

As far as I know these are the only two options at the moment.  If you
are happy patching the matplotlib source then you could use this patch I
wrote a while ago which implements an arrowhead line marker (specify
'-a' as the style in a plot command or use the keyword argument
marker="a", linestyle="-").  This patch is limited in that if you make
the linewidth greater than around 1 the end of the line will be visible
after the last arrow.  Unfortunately to fix this would require doing
something more than just implementing a new marker style.

Nicholas Young

Hi Eric,

On Tue, 29 Nov 2005, Eric Emsellem wrote:

> Hi,
> I have installed python2.4, the last versions of scipy and numarray, and
> matplotlib 0.85.
> I have now constant problems trying to use my scripts, where I often
> make use of arrays.
> It often gives me things like:
>
> ==========
> /usr/lib/python2.4/site-packages/numarray/numarraycore.py:376:
> UserWarning: __array__ returned non-NumArray instance
>   _warnings.warn("__array__ returned non-NumArray instance")
> ---------------------------------------------------------------------------
> numarray.libnumarray.error                                     Traceback
> (most recent call last)
> ...
> error: Type object lookup returned NULL for type -1
> ==========
>
> or similar problems which seems linked to the fact that somehow my
> arrays have :
>
> <type 'scipy.ndarray'>
>
> So if I try to do for example:
>    plot(x,y)
>
> where x and y seem to be scipy.ndarray, it crashes with errors such as
> the one mentioned above.
> (I tried to cast them as numarray.asarray but it keeps its scipy.ndarray
> whatever I do...)

Do you have simple example which reproducibly gives the above error?
(Just to be sure: are you using the new scipy, or the old one?)

Best, Arnd

Hi,
I have installed python2.4, the last versions of scipy and numarray, and 
matplotlib 0.85.
I have now constant problems trying to use my scripts, where I often 
make use of arrays.
It often gives me things like:

==========
/usr/lib/python2.4/site-packages/numarray/numarraycore.py:376: 
UserWarning: __array__ returned non-NumArray instance
  _warnings.warn("__array__ returned non-NumArray instance")
---------------------------------------------------------------------------
numarray.libnumarray.error                                     Traceback 
(most recent call last)
...
error: Type object lookup returned NULL for type -1
==========

or similar problems which seems linked to the fact that somehow my 
arrays have :

<type 'scipy.ndarray'>

So if I try to do for example:
   plot(x,y)

where x and y seem to be scipy.ndarray, it crashes with errors such as 
the one mentioned above.
(I tried to cast them as numarray.asarray but it keeps its scipy.ndarray 
whatever I do...)

So my question is :

- does anybody know what really changed in the last versions of 
scipy/numarray/matplotlib which now induces these crashes (before all 
was fine) ?

- what should I do to solve it (maybe I have to systematically use 
numarray functions by specifying "numarray." in front of all the 
"zeros", "arange" and so on..., but I have the impression this may not 
solve everything) ?

- how do I transform a scipy.ndarray into something compatible for 
matplotlib?

thanks for the help (I realize this is maybe more a numarray/scipy 
question, but maybe someone from the matplotlib crowd can help me: it 
seems that most of my scripts are crashing in similar ways - probably 
bad writing on my side... but I am here to learn..)

Eric

== for info, I use:
matplotlib version 0.85
platform is linux2
numerix numarray 1.4.1
backend GTKAgg version 2.8.0
Python 2.4.1 (#1, Sep 13 2005, 00:39:20)
IPython 0.6.15 -- An enhanced Interactive Python.

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Hi,

I need to draw a sequence of arrows denoting a path. There is the quiver 
function which draws vector fields (and, btw, behaves differently from the 
examples on the web), so this is not an option. Additionally, there is the 
Arrow class. But it is very slow and, what's more important, draws distortet 
arrows at some angles. Am I missing something, or are these two possibilities 
the only options?



Thanks,
wr