I go through a compute loop that takes maybe a few seconds per pass, then plot a new point on the graph. Do I have to? No - I thought mpl was supposed to do this and wanted to learn how. If it really doesn't work I'll do something else.
I don't think animation is correct here - I had the impression animation is where my update would be run as a callback, with a main loop that calls me periodically. Could that fit the model I described, where a lengthy computation produces a new value every few/10s of seconds?
On Mon, Mar 11, 2013 at 1:55 PM, David Hoese <dhoese@...287... > <mailto:dhoese@…287…>> wrote:
Someone may have to correct me, but I think this has to do with
the Qt4 event loop and it not being run properly. When you get
into real time plotting it can get kind of tricky. In your case (I
got the same results). I have made real-time PyQt4 GUIs before and
have always used separate QThreads and Qt signals/slots to update
the plot. I've never used GTK so I'm not sure why that worked vs
Qt, I would think they would use similar principles but matplotlib
does some magic behind the scenes sometimes. You can see different
results if you comment out the while loop and import the module
into your python/ipython interpreter. After doing this you'll see
the figure pop up (you don't even need the fig.canvas.show() for
this part if interactive mode is on. I went one step further and
turned the while loop into a function:
def one_iter(i):
# Contents of while loop
Calling this in the interpreter shows the figure updating after
each call, but running in a loop (even with sleep) won't show any
updates until the loop is done. In my opinion you have a few
choices that really depend on your programming comfort level:
1. Don't make a real-time plot.
Do you really need a real-time plot that updates from some
external source?
2. Maybe you should look at the matplotlib animation functionality
(http://matplotlib.org/api/animation_api.html). I like this
tutorial:
http://jakevdp.github.com/blog/2012/08/18/matplotlib-animation-tutorial/.
This won't get you a real-time GUI exactly, but it can help if
what you're doing isn't too complicated. It can also be nice for
making videos of plot animations.
3. If you need a GUI with multiple plots and you need for future
feature creep, I would research making PyQt4 GUIs, QThreads, Qt
signals and slots, and putting matplotlib figures into a PyQt4
GUI. This is complex if you are not familiar with GUI programming
and will take a while.
Sorry I couldn't be of more help, but it really depends on what
exactly you are doing. Mainly, what do you mean by real-time? Do
you really mean animation? Let me know what you come up with, I'm
interested.
-Dave
P.S. Why use a while loop? You can do the same thing with:
for i in range(1000):
# Do stuff
On 3/11/13 10:34 AM, Neal Becker wrote:
I added fig.canvas.show(). It still does nothing.
If I add
mpl.use ('GTK'), now it seems to be doing realtime plotting.
import matplotlib as mpl
import matplotlib.pyplot as plt
plt.ion()
import numpy as np
fig=plt.figure()
plt.axis([0,1000,0,1])
i=0
x=list()
y=list()
fig.canvas.show()
while i <1000:
temp_y=np.random.random()
x.append(i)
y.append(temp_y)
plt.scatter(i,temp_y)
i+=1
plt.draw()
On Mon, Mar 11, 2013 at 10:35 AM, David Hoese <dhoese@...287... >> <mailto:dhoese@…287…>> wrote:
Oops forgot to change the subject line.
On 3/11/13 9:34 AM, David Hoese wrote:
You likely need to "show()" the canvas. I usually do this
by calling "fig.canvas.show()" before the for loop.
Since you are using a Qt4 backend the canvas used by the
figure is a QWidget, the basic component of a Qt4 GUI. I
don't know if there is a more matplotlib specific way of
doing this, but when dealing with a larger system this is
how I do it.
I would also add a sleep ("from time import sleep") of a
couple seconds for testing to make sure you are getting
through the entire for loop before you can see it.
Please CC in any replies, thanks.
-Dave
On 3/11/13 8:58 AM, ndbecker2@...287... >> <mailto:ndbecker2@…287…> wrote:
I want to update a plot in real time. I did some
goog search, and saw various
answers. Trouble is, they aren't working.
Here's a typical example:
import matplotlib.pyplot as plt
import numpy as np
fig=plt.figure()
plt.axis([0,1000,0,1])
i=0
x=list()
y=list()
while i <1000:
temp_y=np.random.random()
x.append(i)
y.append(temp_y)
plt.scatter(i,temp_y)
i+=1
plt.draw()
If I run this, it draws nothing.
This is my matplotlibrc:
backend : Qt4Agg
mathtext.fontset: stix