Animating a Quadmesh from pcolormesh with matplotlib

Question

As a result of a full day of trial and error, I'm posting my findings as a help to anyone else who may come across this problem.

For the last couple days, I've been trying to simulate a real-time plot of some radar data from a netCDF file to work with a GUI I'm building for a school project. The first thing I tried was a simple redrawing of the data using the 'interactive mode' of matplotlib, as follows:

import matplotlib.pylab as plt

fig = plt.figure()
plt.ion() #Interactive mode on
for i in range(2,155): #Set to the number of rows in your quadmesh, start at 2 for overlap
    plt.hold(True)
    print i
    #Please note: To use this example you must compute X, Y, and C previously.
    #Here I take a slice of the data I'm plotting - if this were a real-time
    #plot, you would insert the new data to be plotted here.
    temp = plt.pcolormesh(X[i-2:i], Y[i-2:i], C[i-2:i])
    plt.draw()
    plt.pause(.001) #You must use plt.pause or the figure will freeze

 plt.hold(False)      
 plt.ioff() #Interactive mode off

While this technically works, it also disables the zoom functions, as well as pan, and well, everything!

For a radar display plot, this was unacceptable. See my solution to this below.

Answer 1

So I started looking into the matplotlib animation API, hoping to find a solution. The animation did turn out to be exactly what I was looking for, although its use with a QuadMesh object in slices was not exactly documented. This is what I eventually came up with:

import matplotlib.pylab as plt
from matplotlib import animation

fig = plt.figure()

plt.hold(True)
#We need to prime the pump, so to speak and create a quadmesh for plt to work with
plt.pcolormesh(X[0:1], Y[0:1], C[0:1])

anim = animation.FuncAnimation(fig, animate, frames = range(2,155), blit = False)

plt.show()
plt.hold(False)

def animate( self, i):
    plt.title('Ray: %.2f'%i)
    #This is where new data is inserted into the plot.
    plt.pcolormesh(X[i-2:i], Y[i-2:i], C[i-2:i])

Note that blit must be False! Otherwise it will yell at you about a QuadMesh object not being 'iterable'.

I don't have access to the radar yet, so I haven't been able to test this against live data streams, but for a static file, it has worked great thus far. While the data is being plotted, I can zoom and pan with the animation.

Good luck with your own animation/plotting ambitions!