方法
random.RandomState.
dirichlet
从Dirichlet分布中提取样本。
画 size Dirichlet分布的维数k的样本。Dirichlet分布的随机变量可以看作Beta分布的多元推广。狄里克莱分布是贝叶斯推理中多项式分布的共轭先验。
注解
新代码应该使用 dirichlet A方法 default_rng() 请参阅 快速启动 .
default_rng()
分布参数(长度 k 长度样品 k )
k
输出形状。如果给定的形状是,例如, (m, n) 然后 m * n * k 抽取样品。默认值为“无”,在这种情况下为长度向量 k 返回。
(m, n)
m * n * k
提取的样品,形状 (size, k) .
(size, k)
如果有任何值 alpha 小于或等于零
alpha
参见
Generator.dirichlet
应该用于新代码。
笔记
Dirichlet分布是向量上的分布 符合条件的 和 .
概率密度函数 一类Dirichlet分布随机向量的性质 与…成比例
System Message: WARNING/2 (p(x)\propto\prod{i=1}^{k}{x^{\alpha{i-1}}u i},)
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在哪里? 是包含正浓度参数的向量。
该方法使用以下属性进行计算:let 是一个随机向量,其分量遵循标准伽马分布,然后 狄利克雷分布吗
工具书类
David McKay,“信息理论、推理和学习算法”,第23章,http://www.interrunce.org.uk/mackay/itila/
维基百科,“dirichlet distribution”,https://en.wikipedia.org/wiki/dirichlet_distribution
实例
以维基百科中引用的一个例子为例,如果要将字符串(每个初始长度为1.0)切割成具有不同长度的k个片段,则可以使用这种分布,其中每个片段平均具有指定的平均长度,但允许片段的相对大小发生一些变化。
>>> s = np.random.dirichlet((10, 5, 3), 20).transpose()
>>> import matplotlib.pyplot as plt >>> plt.barh(range(20), s[0]) >>> plt.barh(range(20), s[1], left=s[0], color='g') >>> plt.barh(range(20), s[2], left=s[0]+s[1], color='r') >>> plt.title("Lengths of Strings")