Hi Xavier (cc list),

It may be a bug, however I do not know what the default behaviour 'should' be. 
You could do:

lims = [-4, 4, -4, 4]
axis(lims)

after calling quiver to see the whole arrow. I did notice that calling

axis('tight')

threw the following error

/Users/Damon/python/lib/matplotlib/axes.py:2038: UserWarning: Attempting to set 
identical xmin==xmax results in singular transformations; automatically 
expanding.  xmin=1.0, xmax=1.0
  warnings.warn('Attempting to set identical xmin==xmax results in singular 
transformations; automatically expanding.  xmin=%s, xmax=%s'%(xmin, xmax))
/Users/Damon/python/lib/matplotlib/axes.py:2212: UserWarning: Attempting to set 
identical ymin==ymax results in singular transformations; automatically 
expanding.  ymin=1.0, ymax=1.0
  warnings.warn('Attempting to set identical ymin==ymax results in singular 
transformations; automatically expanding.  ymin=%s, ymax=%s'%(ymin, ymax))

is this correct, or is it a bug? I'm using "ipython -pylab" with the MacOSX 
backend. I was expecting axis('tight') would scale the axes so I could see the 
whole arrow.


Regards,
-- Damon

--------------------------
Damon McDougall
Mathematics Institute
University of Warwick
Coventry
CV4 7AL
d.mcdoug...@warwick.ac.uk

On 22 Nov 2009, at 21:34, Xavier Gnata wrote:

> Hi,
> 
> RTFM...indeed it works.
> However, the axis do not scale accordingly:
> 
> quiver([1],[1],[2],[2], angles='xy', scale_units='xy', scale=1) on a TkAgg 
> backend produce a plot with:
> In [11]: axis()
> Out[11]:
> (0.94000000000000006,
> 1.0600000000000001,
> 0.94000000000000006,
> 1.0600000000000001)
> 
> The display area scales the same way as it does using quiver([1],[1],[2],[2]) 
> (without any other args).
> It looks like a bug.
> 
> Xavier
> 
> 
>> Hi Xavier,
>> 
>> You can pass some handy keyword arguments to fix that. Use the following:
>> 
>> quiver([1],[1],[1.2],[1.2], angles='xy', scale_units='xy', scale=1)
>> 
>> Hope that helps :)
>> 
>> 
>> Regards,
>> -- Damon
>> 
>> --------------------------
>> Damon McDougall
>> Mathematics Institute
>> University of Warwick
>> Coventry
>> CV4 7AL
>> d.mcdoug...@warwick.ac.uk
>> 
>> On 22 Nov 2009, at 16:37, Xavier Gnata wrote:
>> 
>>   
>>> Hi,
>>> 
>>> I woud like to draw a vector field using pylab.
>>> quivert looks nice but it sould not scale the arrows to fit my use-case.
>>> quiver([1],[1],[1.2],[1.2]) does plot a nice arrow but the head of the
>>> arrow is not at (1.2,1.2).
>>> Is there a way to plot a list of arrows *without* any scaling?
>>> 
>>> Xavier
>>> 
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