Re: [Matplotlib-users] dynamic update in TkAgg ? (more)

[Stephen R. <rod...@ss...>]

> I agree.  The current design of matplotlib doesn't really support this
> kind of use because it redraws the entire figure every time and does
> too much duplicate work at the python level.  It shouldn't be too hard
> to add some specialized functions for agg that support strip charts.
> I've been planning to do it because we have a need for it here, and
> there is some general on c.l.python for this kind of plotting feature
> in python.
>
> So I can start mulling over the design, can you tell me what kinds of
> real time updates you need - only solid lines or arbitrary symbols
> like 'o' too?  Anything else besides line plots?
>
> I'm envisioning some extension code that talks directly to the data
> source and to the agg backend, updating only part of the canvas.  The
> blitting functions for GTK/WX/Tk Agg would have to be extended to blit
> only a region of the canvas.

We'd also be interested in updates to real-time graph capabilities. 
We've just started examining Python + wxPython as a platform for 
control of some of our robotic systems. I've gotten a real-time bar 
graph running now, but it's awfully inefficient. I modified the basic 
dynamic_demo_wx.py file to update regularly, and at a forced 10 FPS it 
locks out the wxPython interface on my dual 2 GHZ Mac G5. No way it 
should do that ...

We'd also be interested in strip charts, mostly line based. We'd want 
to do multiple lines per chart. A capability to move through time, or 
zooming, might be useful, but certainly not necessary in a first rev 
(just mentioning it for now).

For bar graphs, we have to update at a given rate (typically up to 
about 25Hz), with different colors per bar (I have yet to do this part 
in the example I'm working on - think of multilpe temperatures being 
displayed, and different colors indicating different zones, per bar; 
nominal, caution, danger).

Having said all that, we're currently  using wxPython, and I don't yet 
understand how AGG fits in the picture with matplotlib. :-(

TIA
Stephen