如何动态更新matplotlib刻度标签

Question

I have an animated graph that gets Network usage history and scales the y limits dynamically depending on the magnitude of the relevant data being passed. How do I get my y tick labels to reflect the changing y limits? Everything works fine when I set blit=Flase everything updates fine however I don't want everything to update every tick, just the y tick labels when the y limits change? So how do I just update or redraw the y tick labels?

def resize(self, y_data):
    cur_max = max(y_data)
    if cur_max > self.ax.get_ylim()[1]:  # if cur_max > upper y limit..
        self.ax.set_ylim(-1, cur_max + cur_max * .10)  # increase upper y limit to fit cur_max
        ### update/redraw tick labels? ###
    if self.ax.get_ylim()[1] * .25 > cur_max > 0:  # if 1/4 the upper y limit > cur_max and cur_max > 0...
        self.ax.set_ylim(-1, cur_max * .50)  # set upper y limit 1/2 its current size
        ### update/redraw tick labels? ###

Answer 1

I guess what you need is to chose an appropriate tick locator and/or tick formatter : a function that is called to dynamically relocate the ticks and labels when the axis limits are changed.

all docs can be found here : http://matplotlib.org/api/ticker_api.html

You can use predefined locators (eg LinearLocator) or define your own locator following the example below :

import matplotlib.pyplot as plt
from matplotlib import ticker
import numpy as np

#- define the data
x = np.linspace(0., 1., 100)
y = np.random.randn(len(x))

#- plot it
ax = plt.gca()
ax.plot(x, y, 'k')

#- define your own locator based on ticker.LinearLocator
class MyLocator(ticker.LinearLocator):
   def tick_values(self, vmin, vmax):
       "vmin and vmax are the axis limits, return the tick locations here"
       return [vmin, 0.5 * (vmin + vmax), vmax]

#- initiate the locator and attach it to the current axis
ML = MyLocator()
ax.yaxis.set_major_locator(ML)

plt.show()
#- now, play with the zoom to see the y-ticks changing