Re: [Matplotlib-users] Apparent bug in Data limits with LineCollections

[Christopher B. <Chr...@no...>]

Eric Firing wrote:
>> I'm having problems with the data limits when I use a LineCollection
>>
>> Here is the relevant code. A VectorLinecollection is a subclass of 
>> LineCollection. ax is an Axes instance.
>>
>>         ax.clear()
>>         VLC  = VectorLineCollection(t, y, theta, self.Figure, ax)
>>         ax.add_collection(VLC)
>>         ax.plot(t, y, 'o')
>>         print "The lines are:", ax.get_lines()
>>         print "AutoScaleOn:", ax._autoscaleon
>>         print  ax.dataLim.intervaly()
>>         print ax.dataLim.intervaly().get_bounds()
>>         ax.autoscale_view()
>>

> It is not entirely clear to me what you mean by "call it again...",

Sorry about that. this code is in a method, and when I call that method 
again, it gets re-run, but with different data. What I want to happen is 
for the axis to auto-scale to the new data.

> but 
> note that autoscale_view() updates the viewLim from the dataLim; it does 
> not update the dataLim.

exactly. That's why I've printed ax.dataLim.intervaly().get_bounds(). 
dataLim is not getting updated each time this code is run.

>  That is done by add_line, which is called by 
> plot,

It looks like it should first get updated by the axes,.clear() call, 
then updated again each time you add something to the axes.

> but it is not done by add_collection, as far as I can see.

except that it works fine the first time this code is run: 
add_collection seems to update dataLim, but the clear call doesn't clear 
it out again.

In this case, the problem is that I run this code with large data, the 
axis limits get set to large values. then I run it again with smaller 
values data, and the axis limits stay large, even after calling clear() 
and autoscale_view().

> axes methods for updating dataLim are:

I saw those, but I don't know where they are getting called. most 
importantly, I don't know what is happening to dataLim in a clear() 
call, but it doesn't seem to be working right.

Maybe I'll try to make a small sample that demonstrates the issue. stay 
tuned.

-Chris



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Chr...@no...