Embedding matplotlib graph on Tkinter GUI

Question

Good evening every... am learning how to embed matplotlib graph on Tkinter GUI and am not succeeding and I have attached a picture to show you what's happening, please help. Am getting data from the Arduino serial port (ECG readings), plot it with matplotlib(embedded on Tkinter GUI) but when I run my code below a matplotlib figure is created where the plot is happening.

NOTE THAT MY AIM IS TO PLOT DIRECT ON THE GRAPH THAT IS ON THE GUI AND DON'T WORRY ABOUT THE GRAPH BEEN PLOTTED.

[![enter image description here][1]][1]import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import (FigureCanvasTkAgg, NavigationToolbar2Tk)
from matplotlib.figure import Figure
import numpy as np
import serial as sr
import time


def start_plot():
    data = np.array([])
    while True:
        a = s.readline()
        a.decode()
        b = float(a[0:4])
        data = np.append(data, b);
        plt.cla()
        plt.plot(data)
        plt.pause(0.01)
    s.close()

main_window = Tk()
main_window.configure(background='light blue')
main_window.iconbitmap('lardmon_icon.ico')
main_window.title("ECG-LArdmon")
main_window.geometry('800x700')
main_window.resizable(width=False, height=False)




plotting_frame = LabelFrame(main_window, text='Real Time', bg='white', width=300, height=440, bd=5, relief=SUNKEN)
controls_frame = LabelFrame(main_window, text='Controls', background='light grey', height=150)

controls_frame.pack(fill='both', expand='1', side=TOP, padx=20, pady=10)
plotting_frame.pack(fill='both', expand='yes', side=BOTTOM, padx=20)


start_button = Button(controls_frame, text='Start Monitoring', width=16, height=2, borderwidth=3, command=start_plot)
start_button.pack(side=LEFT, padx=26)

exit_button = Button(controls_frame, text='Close', width=10, height=2, borderwidth=3, command=main_window.destroy)
exit_button.pack(side=RIGHT, padx=26)



s = sr.Serial('COM3', 9600)
fig = Figure()
ax = fig.add_subplot(111)
ax.set_title("Electrocadiogram")
ax.set_xlabel("Time(Sec)")
ax.set_ylabel("Voltage(mV)")
ax.set_xlim(0, 200)
ax.set_ylim(-0.5, 6)
ax.grid(b=True, which='major', color='#666666', linestyle='-')
ax.minorticks_on()
ax.grid(b=True, which='minor', color='#666666', linestyle='-', alpha=0.2)
canvas = FigureCanvasTkAgg(fig, master=plotting_frame)
canvas.get_tk_widget().place(x = 0, y = 0, width = 600, height = 420)
canvas.draw()

main_window.mainloop()

Reason is simple: your function is not plotting on the Figure and ax you already created. Instead, you are calling plt.plot, which creates a new instance and also runs on a separate thread. Also note that a while loop will freeze your GUI. — Henry Yik
– Henry Yik, Commented Oct 16, 2021 at 17:41
@HenryYik that's where am getting confused, how can I go about fixing it? — Kennerdol
– Kennerdol, Commented Oct 16, 2021 at 18:57

Henry Yik · Accepted Answer · 2021-10-17 13:29:07Z

2

You already created a Figure object and an ax, so always plot on it and update your canvas.
Use tkinter.after method to call your function recursively so it won't freeze your GUI.

Below are the minimum changes required to showcase how it can be done:

import matplotlib.pyplot as plt
from matplotlib.backends.backend_tkagg import (FigureCanvasTkAgg, NavigationToolbar2Tk)
from matplotlib.figure import Figure
import numpy as np

from tkinter import *

data = []

def start_plot():
    data.append(np.random.uniform(0, 5))
    ax.plot(data, color="blue")
    canvas.draw_idle()
    main_window.after(100, start_plot) # in milliseconds, 1000 for 1 second

# no change to the rest
....

answered Oct 17, 2021 at 13:29

Henry Yik

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1 Comment

Kennerdol Over a year ago

Thank brother for the help you've really saved my life and blessings all the way.

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