2D Animation in XY plane using Scatter

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It is a Python 2D, 3D plotting library which draw high quality figures.

matplotlib
URL: http://matplotlib.org/

Summary:
This article is written about matplotlib.
I show you how to create an animation using the scatter.
In scatter, you can update the coordinates of the points by using the set_offsets method.

I show example python script.
This script is plotting three points in xy coordinates.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import numpy as np

def _update_plot(i, fig, scat):
    scat.set_offsets(([0, i],[50, i],[100, i]))
    print('Frames: %d' %i)

    return scat,

fig =  plt.figure()                

x = [0, 50, 100]
y = [0, 0, 0]

ax = fig.add_subplot(111)
ax.grid(True, linestyle = '-', color = '0.75')
ax.set_xlim([-50, 200])
ax.set_ylim([-50, 200])

scat = plt.scatter(x, y, c = x)
scat.set_alpha(0.8)

anim = animation.FuncAnimation(fig, _update_plot, fargs = (fig, scat),
                               frames = 100, interval = 100)
              
plt.show()

Flow of a process.

1. Import the required method.

import matplotlib.pyplot as plt
import matplotlib.animation as animation
import numpy as np

2. Define a callback function.

def _update_plot(i, fig, scat):
    scat.set_offsets(([0, i],[50, i],[100, i]))
    print('Frames: %d' %i)

    return scat,

Note:
In instantiate scatter, value of X and Y is set [x1, x2, ..., xN], [y1, y2, ..., yN].
But in set_offsets method, you set as follows.


set_offsets(([x1, y1], [x2, y2], ...., [xN, yN]))

3. Instantiate the Figure Object.

fig =  plt.figure()

4. Sets the value of the X and Y.

x = [0, 50, 100]
y = [0, 0, 0]

5. Instantiate the Subplot Object.

ax = fig.add_subplot(111)

6. Sets a grid and a limits of the X and Y.

ax.grid(True, linestyle = '-', color = '0.75')
ax.set_xlim([-50, 200])
ax.set_ylim([-50, 200])

7. Instantiate the Scatter Object.

scat = plt.scatter(x, y, c = x)

x:X-axis values.
[x1, x2, ..., xN]
y:Y-axis values.
[y1, y2, ..., yN]
c:Color
It changes according to the value of the X axis.


set_offsets(([x1, y1], [x2, y2], ...., [xN, yN]))

8. Sets a Alpha Channel of the points.

scat.set_alpha(0.8)

9. Instantiate the FuncAnimation Object.

anim = animation.FuncAnimation(fig, _update_plot, fargs = (fig, scat),
                               frames = 100, interval = 100)

fig: Figure Object
_update_plot: Callback Function
fargs: Value to be passed to the callback function
frams: Number of frames
interval: Call interval of the callback function


10. Start the Animation.

plt.show()

Movie:



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