Z 表

此包提供标准正态表的查找函数，也称为 Z 表。因为查找函数是 const fn，它们可以在编译时评估。此包是

• 小型
• 快速，因为它依赖于简单的表查找并且可以在编译时评估
• 极简主义，仅提供一些基本的表查找函数

请注意，此包不是最精确的，因为它仅依赖于表查找。

如果您需要更精确且功能更强大的东西，请不要使用此包。一个替代方案是 statrs。

示例

use z_table::{lookup_with, reverse_lookup_with};

fn main() {
    // Some birth weights of newborns in kg.
    let birth_weights: [f32; 5] = [2.5, 2.7, 3.1, 3.4, 3.6];
    let n = birth_weights.len() as f32;
    // Calculate the average weight of a newborn.
    let mean: f32 = birth_weights.iter().sum::<f32>() / n;
    // Calculate the variance and standard derivation.
    let variance: f32 = birth_weights.iter().map(|x| x.powi(2)).sum::<f32>() / n - mean.powi(2);
    let standard_derivation = variance.sqrt();

    println!(
        "The probability of a newborn to weight less than 3.5 kg is {} %",
        lookup_with(3.5, mean, standard_derivation) * 100.0
    );

    println!(
        "The weight of a newborn is with a 90 % probability under {} kg",
        reverse_lookup_with(0.9, mean, standard_derivation)
    );
}

输出为

The probability of a newborn to weight less than 3.5 kg is 85.54277 %
The weight of a newborn is with a 90 % probability under 3.588379 kg