# beta_cdf()beta_cdf()

``````beta_cdf(0.2, 10.0, 50.0)
``````

probability = `beta_cdf(`x ,...`)`，则 `beta_inv(`probability ,...`)` = xIf probability = `beta_cdf(`x ,...`)`, then `beta_inv(`probability ,...`)` = x.

Beta 分布通常用于研究样本中某个因素的变化情况（用百分数表示），如一天中人们看电视所花时间的比例。The beta distribution is commonly used to study variation in the percentage of something across samples, such as the fraction of the day people spend watching television.

## 语法Syntax

`beta_cdf(`x`, `alpha`, `beta`)``beta_cdf(`x`, `alpha`, `beta`)`

## 参数Arguments

• x：用于计算函数的值。x : A value at which to evaluate the function.
• alpha：分布的一个参数。alpha : A parameter of the distribution.
• beta：分布的一个参数。beta : A parameter of the distribution.

## 返回Returns

• 累积 beta 分布函数。The cumulative beta distribution function.

## 示例Examples

``````datatable(x:double, alpha:double, beta:double, comment:string)
[
0.9, 10.0, 20.0, "Valid input",
1.5, 10.0, 20.0, "x > 1, yields NaN",
double(-10), 10.0, 20.0, "x < 0, yields NaN",
0.1, double(-1.0), 20.0, "alpha is < 0, yields NaN"
]
| extend b = beta_cdf(x, alpha, beta)
``````
xx alphaalpha betabeta commentcomment bb
0.90.9 1010 2020 有效输入Valid input 0.9999999999999590.999999999999959
1.51.5 1010 2020 x > 1，生成 NANx > 1, yields NaN NaNNaN
-10-10 1010 2020 x < 0，生成 NANx < 0, yields NaN NaNNaN
0.10.1 -1-1 2020 alpha < 0，生成 NANalpha is < 0, yields NaN NaNNaN