[Bug]: Animation was deleted without rendering anything

[vivimagprime]

Bug summary

I dont know why I am getting this error. My objective is to do real time plotting in python from arduino. Please help :)

Code for reproduction

import serial
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import csv

# Constants
SERIAL_PORT = 'COM7'
BAUD_RATE = 9600

# Initialize serial connection
ser = serial.Serial(SERIAL_PORT, BAUD_RATE)

# Initialize empty lists to store data
x_vals = []
sensorValue1_data = []

# Create a function to read and process data from Arduino
def read_and_process_data():
    line = ser.readline().decode('utf-8').strip()
    sensorValues = line.split(', ')

    x_vals.append(float(sensorValues[0]))
    sensorValue1_data.append(int(sensorValues[1]))

    # Print the received values
    print(f'Time: {sensorValues[0]}, distance: {sensorValues[1]}')

# Create a function to update the plot
def update_plot(frame):
    read_and_process_data()
    plt.cla()
    plt.plot(x_vals, sensorValue1_data, label='Sensor 1')
    plt.xlabel('Time')
    plt.ylabel('distance')
    plt.legend()

# Create a function to save data to a CSV file when the plot window is closed
def on_close(event):
    with open('arduino_data.csv', 'w', newline='') as csvfile:
        writer = csv.writer(csvfile)
        writer.writerow(['Time', 'Sensor1', 'Sensor2'])
        for x, s1 in zip(x_vals, sensorValue1_data):
            writer.writerow([x, s1])

# Register the callback function for when the plot window is closed
fig, ax = plt.subplots()
fig.canvas.mpl_connect('close_event', on_close)

ani = FuncAnimation(fig, update_plot, interval=10)
plt.show()

Actual outcome

runfile('C:/Users/user/Desktop/live_plot_arduino.py', wdir='C:/Users/user/Desktop')
C:\Users\user\anaconda3\lib\site-packages\matplotlib\animation.py:973: UserWarning: Animation was deleted without rendering anything. This is most likely unintended. To prevent deletion, assign the Animation to a variable that exists for as long as you need the Animation.
warnings.warn(

Expected outcome

I should be getting a live plotting of the data. I am just measuring distance with time and I want that to be plotted.

Additional information

No response

Operating system

windows

Matplotlib Version

3.4.3

Matplotlib Backend

No response

Python version

No response

Jupyter version

No response

Installation

None

[timhoffm]

Please boil down your problem to a minimal working example. We cannot test your code with a serial device.

When stripping down your code, it works:

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


# Initialize empty lists to store data
x_vals = []
sensorValue1_data = []

# Create a function to read and process data from Arduino
def read_and_process_data():
    xn = len(x_vals)+1
    x_vals.append(xn)
    sensorValue1_data.append(np.sin(xn))
    print("read done")


# Create a function to update the plot
def update_plot(frame):
    read_and_process_data()
    plt.cla()
    plt.plot(x_vals, sensorValue1_data, label='Sensor 1')
    plt.xlabel('Time')
    plt.ylabel('distance')
    plt.legend()

# Create a function to save data to a CSV file when the plot window is closed
def on_close(event):
    print("write, write, write")

# Register the callback function for when the plot window is closed
fig, ax = plt.subplots()
fig.canvas.mpl_connect('close_event', on_close)

ani = FuncAnimation(fig, update_plot, interval=1)
plt.show()

---

General hint: Note that it's faster to not clear and redraw everyting in the update function. Instead, only set_data() add additional data points and update the limits if needed. See e.g. https://matplotlib.org/devdocs/gallery/animation/animate_decay.html