Multiple plots on same chart - Matplotlib

Question

I'm plotting real-time data using parsed data from a file that is being repeatedly opened. I'm deriving and plotting two different values on the same chart. The Y axis scales up and down according the values of each. The "snr" (green) value is plotting fine but the "data_rate"(red) value seems to be static. See screenshot.

import matplotlib.pyplot as plt
import csv
import datetime
from matplotlib.animation import FuncAnimation
import numpy as np


x = []
y = []
z = []

rssi_val = []

def animate(i):
    with open('stats.txt', 'r') as searchfile:
        time = (searchfile.read(8))
        for line in searchfile:
            if 'agrCtlRSSI:' in line:
                rssi_val = line[16:20]
                rssi_val=int(rssi_val)
            if 'agrCtlNoise:' in line:
                noise_val = (line[16:20])
                noise_val=int(noise_val)
            if 'maxRate:' in line:
                data_rate = (line[16:20])
                data_rate=int(data_rate)


    snr = ((noise_val - rssi_val) * -1)
    #begin test
    y.append(snr)
    x.append(time)
    z.append(data_rate)
    #end test

#begin test
    plt.cla()

    #Verify values are not empty
    print("SNR = ", snr)
    print("DR = ", data_rate)

    plt.plot(snr,label='Signal')
    plt.plot(data_rate,label='Data Rate')

    plt.legend(loc='upper right')

    plt.plot(x,y,z)



    ax=plt.gca()
    ax.tick_params('x',labelrotation=60)
#end test

ani = FuncAnimation(plt.gcf(), animate, interval=1000)

plt.show()

Answer 1

The simplest way is to call plot twice.

plt.plot(x,y)
plt.plot(x,z)

See "Plotting multiple sets of data" here for more options.