Animate text within a circle - Matplotlib - pandas

Question

The following animates a circle and lines based on a given radius. I'm hoping combine the plot with animated text highlighting different segments within this circle. The text does get updated for each new frame but it doesn't remove the previous frames text.
Note: I'm trying to keep the animate function as I want to keep the axis the same and only animate updated data.
import pandas as pd
import matplotlib.pyplot as plt
import numpy as np
from matplotlib import animation
import matplotlib.gridspec as gridspec
import math
df = pd.DataFrame({
'Time' : [1,1,1,1,2,2,2,2,3,3,3,3],
'X2' : [0,0,0,0,-1,-1,-1,-1,0,0,0,0],
'Y2' : [0,0,0,0,1,1,1,1,1,1,1,1],
'Angle' : [0,0,0,0,-45,-45,-45,-45,90,90,90,90],
})
fig = plt.figure(figsize = (8,10))
grid = gridspec.GridSpec(1, 2)
gridsize = (1, 2)
ax = plt.subplot2grid(gridsize, (0, 0))
ax2 = plt.subplot2grid(gridsize, (0, 1))
ax2.set_xlim(-10, 10)
ax2.set_ylim(-10, 10)
# the center of the compass
moving_x = np.array(df.groupby(['Time'])['X2'].apply(list))
moving_y = np.array(df.groupby(['Time'])['Y2'].apply(list))
moving_point = ax.scatter(moving_x[0], moving_y[0], c = 'black', marker = 'o', zorder = 3)
radius = df.drop_duplicates(subset = ['Time','X2', 'Y2'])[['X2', 'Y2']].values
circle = plt.Circle(radius[0], 10, color = 'black', fill = False, lw = 0.2)
circle2 = plt.Circle(radius[0], 10, color = 'red', fill = False, lw = 0.2)
ax.add_patch(circle)
ax2.add_patch(circle2)
line1, = ax.plot([],[], color = 'k', linewidth = 1)
line2, = ax.plot([],[], color = 'k', linewidth = 1)
t = df['Angle'][0]
angles = np.array(df.groupby(['Time'])['Angle'].apply(list))
angleText = df.drop_duplicates(subset = ['Time','Angle'])['Angle'].values
rot_mat = lambda theta:np.array([
[np.cos(np.deg2rad(theta)),-np.sin(np.deg2rad(theta))],
[np.sin(np.deg2rad(theta)),np.cos(np.deg2rad(theta))]
])
# compass tags
annotate_tags = ['N','E','S','W']
def animate(i) :
moving_point.set_offsets(np.c_[moving_x[0+i], moving_y[0+i]])
circle.center = (radius[i,0], radius[i,1])
xs1L1=-10.0/2**0.5
ys1L1=10.0/2**0.5
xs2L1=10.0/2**0.5
ys2L1=-10.0/2**0.5
xs1L2=-xs1L1
ys1L2=ys1L1
xs2L2=-xs1L2
ys2L2=ys2L1
cx=radius[i,0]
cy=radius[i,1]
theta=math.radians(angles[i][0])
x1L1=( (xs1L1+radius[i,0] - cx) * math.cos(theta) + (ys1L1+radius[i,1] - cy) * math.sin(theta) ) + cx
x2L1=( (xs2L1+radius[i,0] - cx) * math.cos(theta) + (ys2L1+radius[i,1]- cy) * math.sin(theta) ) + cx
y1L1=( -(xs1L1+radius[i,0] - cx) * math.sin(theta) + (ys1L1+radius[i,1] - cy) * math.cos(theta) ) + cy
y2L1=( -(xs2L1+radius[i,0] - cx) * math.sin(theta) + (ys2L1+radius[i,1] - cy) * math.cos(theta) ) + cy
line1.set_data([x1L1,x2L1],[y1L1,y2L1])
x1L2=( (xs1L2+radius[i,0] - cx) * math.cos(theta) + (ys1L2+radius[i,1] - cy) * math.sin(theta) ) + cx
x2L2=( (xs2L2+radius[i,0] - cx) * math.cos(theta) + (ys2L2+radius[i,1]- cy) * math.sin(theta) ) + cx
y1L2=( -(xs1L2+radius[i,0] - cx) * math.sin(theta) + (ys1L2+radius[i,1] - cy) * math.cos(theta) ) + cy
y2L2=( -(xs2L2+radius[i,0] - cx) * math.sin(theta) + (ys2L2+radius[i,1] - cy) * math.cos(theta) ) + cy
line2.set_data([x1L2,x2L2],[y1L2,y2L2])
# Animate compass tags for each frame
tag_pos = np.array([[0,8.5],[8.5,0],[0,-8.5],[-8.5,0]])
tag_pos = tag_pos # rot_mat(angleText[i])
for tag,pos in zip(annotate_tags,tag_pos):
ax.annotate(tag,xy=pos+radius[i], xycoords='data',
fontsize=10,horizontalalignment='right', verticalalignment='bottom')
ani = animation.FuncAnimation(fig, animate, np.arange(0,3), blit = False)

Answer 1

You want to create text objects for as many tags outside the animate function. And, inside the animate function set_text and set_position as shown here:
import pandas as pd
import matplotlib.pyplot as plt
import numpy as np
from matplotlib import animation
import matplotlib.gridspec as gridspec
import math
df = pd.DataFrame({
'Time' : [1,1,1,1,2,2,2,2,3,3,3,3],
'X2' : [0,0,0,0,-1,-1,-1,-1,0,0,0,0],
'Y2' : [0,0,0,0,1,1,1,1,1,1,1,1],
'Angle' : [0,0,0,0,-45,-45,-45,-45,90,90,90,90],
})
fig = plt.figure(figsize = (20,10))
grid = gridspec.GridSpec(1, 2)
gridsize = (1, 2)
ax = plt.subplot2grid(gridsize, (0, 0))
ax2 = plt.subplot2grid(gridsize, (0, 1))
ax2.set_xlim(-10, 10)
ax2.set_ylim(-10, 10)
# the center of the compass
moving_x = np.array(df.groupby(['Time'])['X2'].apply(list))
moving_y = np.array(df.groupby(['Time'])['Y2'].apply(list))
moving_point = ax.scatter(moving_x[0], moving_y[0], c = 'black', marker = 'o', zorder = 3)
radius = df.drop_duplicates(subset = ['Time','X2', 'Y2'])[['X2', 'Y2']].values
circle = plt.Circle(radius[0], 10, color = 'black', fill = False, lw = 0.2)
circle2 = plt.Circle(radius[0], 10, color = 'red', fill = False, lw = 0.2)
ax.add_patch(circle)
ax2.add_patch(circle2)
line1, = ax.plot([],[], color = 'k', linewidth = 1)
line2, = ax.plot([],[], color = 'k', linewidth = 1)
t = df['Angle'][0]
angles = np.array(df.groupby(['Time'])['Angle'].apply(list))
angleText = df.drop_duplicates(subset = ['Time','Angle'])['Angle'].values
rot_mat = lambda theta:np.array([
[np.cos(np.deg2rad(theta)),-np.sin(np.deg2rad(theta))],
[np.sin(np.deg2rad(theta)),np.cos(np.deg2rad(theta))]
])
# compass tags
annotate_tags = ['N','E','S','W']
annotation=[None]*len(annotate_tags)
for i in range(len(annotate_tags)):
annotation[i] = ax.annotate('', xy=(0, 0),xycoords='data',fontsize=10,horizontalalignment='right', verticalalignment='bottom')
def animate(i) :
moving_point.set_offsets(np.c_[moving_x[0+i], moving_y[0+i]])
circle.center = (radius[i,0], radius[i,1])
xs1L1=-10.0/2**0.5
ys1L1=10.0/2**0.5
xs2L1=10.0/2**0.5
ys2L1=-10.0/2**0.5
xs1L2=-xs1L1
ys1L2=ys1L1
xs2L2=-xs1L2
ys2L2=ys2L1
cx=radius[i,0]
cy=radius[i,1]
theta=math.radians(angles[i][0])
x1L1=( (xs1L1+radius[i,0] - cx) * math.cos(theta) + (ys1L1+radius[i,1] - cy) * math.sin(theta) ) + cx
x2L1=( (xs2L1+radius[i,0] - cx) * math.cos(theta) + (ys2L1+radius[i,1]- cy) * math.sin(theta) ) + cx
y1L1=( -(xs1L1+radius[i,0] - cx) * math.sin(theta) + (ys1L1+radius[i,1] - cy) * math.cos(theta) ) + cy
y2L1=( -(xs2L1+radius[i,0] - cx) * math.sin(theta) + (ys2L1+radius[i,1] - cy) * math.cos(theta) ) + cy
line1.set_data([x1L1,x2L1],[y1L1,y2L1])
x1L2=( (xs1L2+radius[i,0] - cx) * math.cos(theta) + (ys1L2+radius[i,1] - cy) * math.sin(theta) ) + cx
x2L2=( (xs2L2+radius[i,0] - cx) * math.cos(theta) + (ys2L2+radius[i,1]- cy) * math.sin(theta) ) + cx
y1L2=( -(xs1L2+radius[i,0] - cx) * math.sin(theta) + (ys1L2+radius[i,1] - cy) * math.cos(theta) ) + cy
y2L2=( -(xs2L2+radius[i,0] - cx) * math.sin(theta) + (ys2L2+radius[i,1] - cy) * math.cos(theta) ) + cy
line2.set_data([x1L2,x2L2],[y1L2,y2L2])
# Animate compass tags for each frame
tag_pos = np.array([[0,8.5],[8.5,0],[0,-8.5],[-8.5,0]])
tag_pos = tag_pos # rot_mat(angleText[i])
k=0
for tag,pos in zip(annotate_tags,tag_pos):
annotation[k].set_text(tag)
annotation[k].set_position(xy=pos+radius[i])
k=k+1
ani = animation.FuncAnimation(fig, animate, np.arange(0,3), blit = False)
ani.save('test.gif', writer='imagemagick', fps=5)
plt.show()