Hi Jae-Joon,
Thanks a ton! The problem is actually not the frequency of changes.
The current method uses draw_artist on each update. However, the time
for draw_artist is linear in the *number* of points so for graphs with
a large amount of data it is extremely inefficient. Your patch means
that update time is linear in the amount of data *updated* and not in
the total amount of data.
As for the ticks you have a point. In my application I actually want
ticks to be shifted (as time goes on) so indeed this is what I want.
In general ticks that are shifted out can be redrawn using set_data
methods which are efficient since a tick can be defined as it's
endpoints. Basically when first calling plot() I set all of the tick
locators to Null and then just add ticks as a line (with two points)
based on the desired spacing. Changing a tick location (or if desired
redrawing it in the same location) is basically a call to
set_(x|y)data and then draw_artist for a line with two points (or a
line collection will *slightly* improve performance if needed).
Anyway, thanks again. I'll play around with it and let you know what I
run into.
Elan
---
I can no other answer make but thanks,
And thanks, and ever thanks.
-- William Shakespeare
On Thu, Apr 23, 2009 at 1:21 PM, Jae-Joon Lee <lee.j.j...@gmail.com> wrote:
> On Mon, Apr 20, 2009 at 4:34 PM, Elan Pavlov <e...@mit.edu> wrote:
>> Hi,
>>
>> I'm trying to use matplotlib for animating data as it is received from an
>> online source (online in the algorithmic sense not internet:). I'd like
>> the graph plot to be updated with high frequency since the data changes
>> rapidly. I've used the BufferRegion with copy_from_bbox / restore_region
>> and it speeds up the plotting considerably but alas it's still not good
>> enough (with a large number of graphs and a large number of data points in
>> each graph).
>>
>
> Well, if you need your plot updated with very high frequency, MPL may
> not be your tool of choice.
> Anyhow, my first recommendation is not to update the plot frequently.
> I mean, do you have to update the plot for every changes? Can you
> update it every 10th change, for example?
>
>> What I'd like to do is to utilize the fact that the animation is updated
>> in a predictable fashion (i.e., scrolling off the screen to the left as
>> new data arrives) in order to speed up the animation. The idea would be to
>> copy the right 99% of the graph (or some other fraction) via some kind of
>> function similar to copy_from_bbox, move it 1% to the left and then plot
>> the new 1% of the data. The problem is that as far as I can tell the
>> copy_from_bbox/restore_region does not actually allow changing the area in
>> which it is restored. I've mucked around in the source files a bit but to
>> no avail.
>>
>> My question is then:
>> 1. Is there some other way to copy everything enclosed in a Bbox? or
>> 2. Is there some way to modify the region in which data reappears when
>> using restore_region?
>> 3. Perhaps I'm missing something?
>>
>> I'm sure someone else has done this since it seems pretty natural and
>> useful for a variety of applications.
>
> I'm attaching a patch that might do what you want to do.
> It implements a "restore_bbox2" method which restores a subset of the
> saved background at a specified position.
> A small example is also attached (it is based on the gtk backend).
>
> I, personally, am not sure if this kind of feature is useful. If you
> shift part of your figure, you have to be careful not to mess up with
> the coordinate system. And also be careful about what to be shifted
> and what to be not (e.g., ticks).
>
> If others find this useful, I'll commit this to the trunk with some
> api improvement.
>
> Regards,
>
> -JJ
>
>
>>
>> Elan
>> ----
>> "If stupidity got us into this mess, why can't it get us out?"
>> - Will Rogers
>>
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