import numpy as np
#import scipy.stats as stats
import seaborn as sns # seaborn package를 이용
import matplotlib.pyplot as plt # matplotlib.pyplot package를 이용
from numpy import random

# set the random seed:
np.random.seed(12345)

r=10000

chi1 = random.chisquare(df=5, size=r)
sns.histplot(data=chi1, x=None).set(title='Histogram of Chi-square w/ df=5')
plt.show()

chi2 = random.chisquare(df=10, size=r)
sns.histplot(data=chi2, x=None).set(title='Histogram of Chi-square w/ df=10')
plt.show()

chi3 = random.chisquare(df=20, size=r)
sns.histplot(data=chi3, x=None).set(title='Histogram of Chi-square w/ df=20')
plt.show()

chi4 = random.chisquare(df=30, size=r)
sns.histplot(data=chi4, x=None).set(title='Histogram of Chi-square w/ df=30')
plt.show()

np.mean(chi1)
np.mean(chi2)
np.mean(chi3)
np.mean(chi4)
print("Mean of Chi-square Distribution w/ df=5 is : ", np.mean(chi1))
print("Mean of Chi-square Distribution w/ df=10 is : ", np.mean(chi2))
print("Mean of Chi-square Distribution w/ df=20 is : ", np.mean(chi3))
print("Mean of Chi-square Distribution w/ df=30 is : ", np.mean(chi4))

np.var(chi1, ddof=1)
np.var(chi2, ddof=1)
np.var(chi3, ddof=1)
np.var(chi4, ddof=1)
print("Variance of Chi-square Distribution w/ df=5 is : ", np.var(chi1, ddof=1))
print("Variance of Chi-square Distribution w/ df=10 is : ", np.var(chi2, ddof=1))
print("Variance of Chi-square Distribution w/ df=20 is : ", np.var(chi3, ddof=1))
print("Variance of Chi-square Distribution w/ df=30 is : ", np.var(chi4, ddof=1))

fig = plt.figure(figsize=(14,7))
# 두 개의 그래프를 한 페이지에 그림
fig, axs = plt.subplots(ncols=2)
fig, ays = plt.subplots(ncols=2)

sns.histplot(data=chi1, x=None, ax=axs[0]).set(title='Histogram of Chi-square w/ df=5 & df=10)')
sns.histplot(data=chi2, x=None, ax=axs[1])
fig.subplots_adjust(wspace=0.5) # 우측그림의 좌우 간격을 조정
#plt.show()
#plt.savefig('C:/BOOK/PyBasics/PyStat/code/chi-1.png')

sns.histplot(data=chi3, x=None, ax=ays[0]).set(title='Histogram of Chi-square w/ df=20 & df=30)')
sns.histplot(data=chi4, x=None, ax=ays[1])
fig.subplots_adjust(wspace=0.5) # 우측그림의 좌우 간격을 조정
plt.show()
#plt.savefig('C:/BOOK/PyBasics/PyStat/code/chi-2.png')