NumPy参考 >例行程序 >Random sampling (numpy.random) >Random Generator > numpy.random.Generator.chisquare
method
Generator.
chisquare
(df, size=None)¶Draw samples from a chi-square distribution.
When df independent random variables, each with standard normal distributions (mean 0, variance 1), are squared and summed, the resulting distribution is chi-square (see Notes). This distribution is often used in hypothesis testing.
Number of degrees of freedom, must be > 0.
Output shape. If the given shape is, e.g., (m, n, k)
, then
m * n * k
samples are drawn. If size is None
(default),
a single value is returned if df
is a scalar. Otherwise,
np.array(df).size
samples are drawn.
Drawn samples from the parameterized chi-square distribution.
When df <= 0 or when an inappropriate size (e.g. size=-1
)
is given.
Notes
The variable obtained by summing the squares of df independent, standard normally distributed random variables:
is chi-square distributed, denoted
The probability density function of the chi-squared distribution is
where is the gamma function,
References
NIST “Engineering Statistics Handbook” https://www.itl.nist.gov/div898/handbook/eda/section3/eda3666.htm
Examples
>>> np.random.default_rng().chisquare(2,4)
array([ 1.89920014, 9.00867716, 3.13710533, 5.62318272]) # random