Python - Exponentially weighted moving average

import matplotlib.pyplot as plt

# Exponentially weighted moving average
# https://medium.com/@abhinav.mahapatra10/beginners-ml-basics-exponentially-weighted-moving-average-8ce3e75768f6

data1 = [25, 28, 26, 22, 19, 23, 27]
data2 = []

a = 0.2
b = 1-a

s = data1[0]
data2.append(s)

for x in data[1:]:
    s = a*x + b*s
    data2.append(s)

plt.plot(data1)
plt.plot(data2)

plt.show()