Python Scatter Plot Multiple Colorbar issue

Question

I am trying to draw scatter plot with dynamic data. I am able to draw the data points through looping; but everytime it creates new colorbar.

Here is my code:

import time
from threading import Thread
import pandas as pd
import matplotlib.pyplot as plt
import random

class RealTime:
    def __init__(self):
        self.flight_complete = True
        self.data = pd.DataFrame(data=None, columns=list('ABC'))
        self.fig=None
        self.axis = None

def on_launch(self):
    plt.ion()
    self.fig = plt.figure()
    self.axis = self.fig.add_subplot(111)

def create_data(self):
    x = round(random.uniform(-1, 1), 2)
    y = round(random.uniform(-1.65, 1.65), 2)
    z = 0.5
    temp_data = pd.DataFrame([[x, y, z]], columns=list('ABC'))
    self.data = self.data.append(temp_data, ignore_index=True)
    # Plot the data
    self.plot()

def start_fly(self):
    self.on_launch()
    fly = Thread(target=self.fly_running)
    fly.start()

def fly_running(self):
    for _ in range(10):
        print("Flying")
        # Create the data
        self.create_data()
        time.sleep(0.1)
    return

def plot(self):
    plt.gca().cla()
    self.data.plot(kind="scatter", x="A", y="B", alpha=0.4,
                        s=50, label="Real Time Position",
                        c="C", cmap=plt.get_cmap("jet"), colorbar=True, ax=self.axis)

    plt.colormaps()
    plt.title("Flight Path Map")
    self.fig.canvas.draw()
    self.fig.canvas.flush_events()


if __name__ == '__main__':
    obj = RealTime()
    obj.on_launch()
    obj.fly_running()

I have read this post : How to retrieve colorbar instance from figure in matplotlib. But I couldn't really work with that.

Do you know why it creates a new colorbar? and how to avoid it?

Best Regards

Answer 1

Panda's plot is creating new colobar because you're asking it to create one (colorbar=True), and it looks like there is now way to tell the function that there is already a colorbar and that it should use that instead.

There are many ways to go around this problem.

the first one would be not not use DataFrame.plot() but instead use matplotlib directly to generate the plot. That will give you more control over the axes that are used and will let you recycle the colorbar from frame to frame. Here are some links that might be relevant:

• How do you add a colormap to a matplotlib Animation?
• Updating the positions and colors of pyplot.scatter

the second option if you want to keep your code close to what it is now it to erase the whole figure at each frame, and let pandas recreate the axes it need every time. i.e.:

def plot(self):
    self.fig.clf()
    self.axis = self.fig.add_subplot(111)
    self.axis = self.data.plot(kind="scatter", x="A", y="B", alpha=0.4,
                               s=50, label="Real Time Position",
                               c="C", cmap=plt.get_cmap("jet"), colorbar=True, ax=self.axis)