04 Missing value given the mean

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import numpy as np
import pandas as pd
from pandas import Series, DataFrame
import matplotlib.pyplot as plt

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x = np.array([5, 2, 2, 4, 8])

sum_num_total = len(x) + 1

sum_total_ = x.sum() # + ? missing

mean = 4

# sum_total/sum_num_total = mean
# sum_total = mean * sum_num_total

missing = mean * sum_num_total - sum_total_

print(missing)

3

# double check

y = np.append(x, [missing])

y.sum() / len(y)

4.0

y.mean()

4.0