通过生成一些随机数据,使用直方图估计概率密度函数。我现在想要两个版本的直方图,即相等的箱宽和相等的箱高直方图。
# -*- coding: utf-8 -*-
from scipy.stats import norm
import matplotlib.pyplot as plt
#import pandas as pd
import numpy as np
fig, ax = plt.subplots(1, 1)
#Calculate a few first moments:
mean, var, skew, kurt = norm.stats(moments='mvsk')
#Display the probability density function (pdf):
x = np.linspace(norm.ppf(0.01),
norm.ppf(0.99), 100)
ax.plot(x, norm.pdf(x),
'r-', lw=5, alpha=0.6, label='norm pdf')
#Freeze the distribution and display the frozen pdf:
rv = norm()
ax.plot(x, rv.pdf(x), 'b-', lw=2, label='frozen pdf')
#Check accuracy of cdf and ppf:
vals = norm.ppf([0.001, 0.5, 0.999])
np.allclose([0.001, 0.5, 0.999], norm.cdf(vals))
#Generate random numbers:
r = norm.rvs(size=10000)
#df = pd.read_excel('ardata.xlsx')
#r = df[['dest','source']].values
#And compare the histogram:
ax.hist(r, density=True, histtype='stepfilled', alpha=0.2)
ax.legend(loc='best', frameon=False)
plt.show()
如果要生成相等的条带宽度和相等的条带高度直方图,则不能使用正态分布的随机样本。为了实现期望的目标,您需要从分布中获取确定性样本。您可以例如:
import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm
fig, ax = plt.subplots(1, 1)
# Display the probability density function (pdf):
xppf = np.linspace(norm.ppf(0.01),
norm.ppf(0.99), 100000)
ax.plot(xppf, norm.pdf(xppf, loc=0),
'r-', lw=3, alpha=0.6, label='norm pdf')
# Create histogram:
mybins = np.linspace(norm.ppf(0.01), norm.ppf(0.99), num=12) # Evenly spaced bins
ax.hist(norm.ppf(xppf, loc=0), bins=mybins, density=True,
histtype='stepfilled', alpha=0.2)
ax.legend(loc='best', frameon=False)
plt.xlabel(r'x')
plt.ylabel(r'PDF(x)')
plt.show()
哪个情节:
从给定的样本数组r
,您可以通过以下方式创建“均匀高度直方图”:
1
,高度乘以宽度应为1
。由于宽度只是从排序元素的第一个到最后一个的范围,因此高度应为其倒数。s = np.sort(r)
bins = 10
ind = np.arange(bins + 1) * (s.size - 1) // bins
ax.bar(s[ind][:-1], 1/(s[-1] - s[0]), width=np.diff(s[ind]),
color='g', alpha=0.4, ec='k', align='edge', zorder=-1, label='equal heights hist')