Question

Python问题我正在处理创建二项式函数的请求，需要四个输入，最后一个是true / false。如果true返回cdf，则默认为true。 if false返回pmf。这是我到目前为止所得到的。有人会告诉我如何完成代码吗？

def binomial_distribution(x,n,p,cum):
  """
  Computes the probability of having x successes out of n trials.
  Each trial has a probability of success p
  """
    nCx = combination(n,x)
    q = 1-p
    return nCx*(p**x)*(q**(n-x))

Answer 1

这是所需的代码。注意事项如下：

def factorial(n): 
    if n == 0: return 1
    factrl = n
    while n > 2:
        n -= 1
        factrl = factrl * n
    return factrl

def combination(n, x):
    return factorial(n)/(factorial(x)*factorial(n-x))

def binomial_distribution(x,n,p,cum = True):
    """
    Computes the probability of having x successes out of n trials.
    Each trial has a probability of success p
    """
    nCx = combination(n,x)
    q = 1-p

    #What helps is a conditional return statement as below
    if cum: return bin_cdf(x, n, p)
    else: return nCx*(p**x)*(q**(n-x))

def bin_cdf(x, n, p):
    cumul = 0.0
    while x > 0:
        print(x)
        cumul += binomial_distribution(x, n, p, False) #Sums using formula
         #This kind of recursion is not only possible but encouraged
        x -= 1
    return cumul

结果已使用第三方计算器验证。另请注意，它不会处理错误。好的程序还测试输入的值是否也有效（例如n总是大于x而p是[0,1]范围内的适当概率值

使用Python的二项分布输出CDF / PMF

1 个答案: