CODEWITHSUNDEEP
pythonmatplotlib
dd24
dd24

Reputation: 29

Live graph in python with a fixed window

I am trying to construct a live graph in python to plot random numbers in a graph with a fixed plot window The width of the plot window will be 20 samples. For the 21st sample, the 1st sample will dissappear from the right side. Here is my code. Cant figure out why is it not plotting.

import random 
import time
import matplotlib.pyplot as plt
import matplotlib.animation as animation
fig = plt.figure()
#creating a subplot 
ax1 = fig.add_subplot(1,1,1)
xs = []
ys = []
iter = 0
def animate(i,xs,ys,iter):
    while True:
        iter = iter+1
        xs.append(iter)
        ys.append(round(random.uniform(-120,20),2))
#I want only 20 data points on the plot i.e the plot window will be only showing 20 samples at a time 
        x = xs[-20:]
        y = ys[-20:]
        ax1.clear()
        ax1.plot(x, y)
        ax1.set_ylim([-120,20])
        plt.xlabel('Value')
        plt.ylabel('Time')
        plt.title('Live Graph')
        time.sleep(1)   

ani = animation.FuncAnimation(fig, animate, fargs = (xs,ys,iter), interval=1000) 
plt.show()

Upvotes: 0

Views: 2265

Answers (1)

Seb
Seb

Reputation: 4576

Check out the documentation for FuncAnimation.

The second parameter is a function that is repeatedly called for each consecutive frame, updating the figure with each call. Your function animate is an infinite loop, so the execution thread never returns back to FuncAnimation. Try something like this instead as a starting point:

import random 
import time
import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig = plt.figure()
ax1 = fig.add_subplot(1,1,1)
xs = []
ys = []
line, = ax1.plot(xs, ys)
plt.xlabel('Value')
plt.ylabel('Time')
plt.title('Live Graph')

def animate(frame, xs, ys):
    xs.append(frame)
    ys.append(round(random.uniform(-120,20),2))
    x = xs[-20:]
    y = ys[-20:]
    line.set_xdata(x)
    line.set_ydata(y)
    ax1.set_xlim(min(x)-1, max(x)+1)
    ax1.set_ylim(min(y)-1, max(y)+1)
    ax1.set_xticks(list(range(min(x), max(x)+1)))
    return line

ani = animation.FuncAnimation(fig, animate, fargs = (xs,ys), interval=100) 
plt.show()

Upvotes: 2

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