Python scipy超載_stats功能測試版分佈

Question

我需要超載_stats函數爲我的測試版分佈。這是我當前的代碼：

from scipy.stats import beta 
import scipy.stats as st 

class CustomBeta(st.rv_continuous): 
    def _stats(self, a, b): 
     # will add own code here 
     mn = a * 1.0/(a + b) 
     var = (a * b * 1.0)/(a + b + 1.0)/(a + b) ** 2.0 
     g1 = 2.0 * (b - a) * sqrt((1.0 + a + b)/(a * b))/(2 + a + b) 
     g2 = 6.0 * (a ** 3 + a ** 2 * (1 - 2 * b) + b ** 2 * (1 + b) - 2 * a * b * (2 + b)) 
     g2 /= a * b * (a + b + 2) * (a + b + 3) 
     return mn, var, g1, g2 

dist = beta(4, 6) 
print dist.rvs() # works fine 


dist = CustomBeta(4, 6) 
print dist.rvs() # crashes 

獲取_rvs()從我的自定義對象給了我很長的堆棧跟蹤和

RuntimeError: maximum recursion depth exceeded

Answer 1

此無關超載_stats錯誤。同樣的行爲可以簡單地通過

class CustomBeta(st.rv_continuous): 
    pass 

dist = CustomBeta(4, 6) 
print(dist.rvs()) # crashes 

的documentation of rv_continuous指出

New random variables can be defined by subclassing the rv_continuous class and re-defining at least the _pdf or the _cdf method.

您將需要提供這些方法中的至少一個來計算概率密度函數（PDF）或累積概率密度引起的函數（CDF）。

此外，

[ rv_continuous ] cannot be used directly as a distribution.

它的用法如下：

class CustomBetaGen(st.rv_continuous): 
    ... 

CustomBeta = CustomBetaGen(name='CustomBeta') 

dist = CustomBeta(4, 6) 

最後，rvs.()似乎並不正確的Beta分佈工作，如果你不提供_rvs方法。

將所有內容放在一起，在偷Beta分佈適當的方法：

from scipy.stats import beta 
import scipy.stats as st 
import numpy as np 

class CustomBetaGen(st.rv_continuous): 
    def _cdf(self, x, a, b): 
     return beta.cdf(x, a, b) 
    def _pdf(self, x, a, b): 
     return beta.pdf(x, a, b) 
    def _rvs(self, a, b): 
     return beta.rvs(a, b) 
    def _stats(self, a, b): 
     # will add own code here 
     mn = a * 1.0/(a + b) 
     var = (a * b * 1.0)/(a + b + 1.0)/(a + b) ** 2.0 
     g1 = 2.0 * (b - a) * np.sqrt((1.0 + a + b)/(a * b))/(2 + a + b) 
     g2 = 6.0 * (a ** 3 + a ** 2 * (1 - 2 * b) + b ** 2 * (1 + b) - 2 * a * b * (2 + b)) 
     g2 /= a * b * (a + b + 2) * (a + b + 3) 
     return mn, var, g1, g2 

CustomBeta = CustomBetaGen(name='CustomBeta') 

dist = beta(4, 6) 
print(dist.rvs()) # works fine 
print(dist.stats()) # (array(0.4), array(0.021818181818181816)) 

dist = CustomBeta(4, 6) 
print(dist.rvs()) # works fine 
print(dist.stats()) # (array(0.4), array(0.021818181818181816))