Automatically Rescale ylim and xlim in Matplotlib

Question

I'm plotting data in Python using matplotlib. I am updating the data of the plot based upon some calculations and want the ylim and xlim to be rescaled automatically. Instead what happens is the scale is set based upon the limits of the initial plot. A MWE is

import random import matplotlib.pyplot as pyplot  pyplot.ion()  x = range(10) y = lambda m: [m*random.random() for i in range(10)]  pLine, = pyplot.plot(x, y(1))  for i in range(10):     pLine.set_ydata(y(i+1))     pyplot.draw() 

The first plot command generates a plot from [0,1] and I can see everything just fine. At the end, the y-data array goes from [0,10) with most of it greater than 1, but the y-limits of the figure remain [0,1].

I know I can manually change the limits using pyplot.ylim(...), but I don't know what to change them to. In the for loop, can I tell pyplot to scale the limits as if it was the first time being plotted?

Answer 1

You will need to update the axes' dataLim, then subsequently update the axes' viewLim based on the dataLim. The approrpiate methods are axes.relim() and ax.autoscale_view() method. Your example then looks like:

import random import matplotlib.pyplot as pyplot  pyplot.ion()  x = range(10) y = lambda m: [m*random.random() for i in range(10)]  pLine, = pyplot.plot(x, y(1))  for i in range(10):     pLine.set_ydata(y(i+1))  ax = pyplot.gca()  # recompute the ax.dataLim ax.relim() # update ax.viewLim using the new dataLim ax.autoscale_view() pyplot.draw()