选择基于百分比加权 [英] selection based on percentage weighting

问题描述

我有一组值，并为每个关联的百分比：

I have a set of values, and an associated percentage for each:

一：70％的几率
B：20％的几率
C：10％的几率

a: 70% chance
b: 20% chance
c: 10% chance

我要选择一个值（A，B，C）根据给定的百分比机会。

I want to select a value (a, b, c) based on the percentage chance given.

我怎么处理这个？

我尝试到目前为止是这样的：

my attempt so far looks like this:

r = random.random()
if r <= .7:
    return a
elif r <= .9:
    return b
else: 
    return c

我卡想出一个算法来处理这​​个问题。我应该如何处理这个所以它可以处理更大值的集合，而不只是串联起来的if-else流动。

I'm stuck coming up with an algorithm to handle this. How should I approach this so it can handle larger sets of values without just chaining together if-else flows.

（任何解释或伪code答案都是精品。一个Python或C＃实现将是非常有用）

(any explanation or answers in pseudo-code are fine. a python or C# implementation would be especially helpful)

推荐答案

下面是在C＃中一个完整的解决方案：

public class ProportionValue<T>
{
    public double Proportion { get; set; }
    public T Value { get; set; }
}

public static class ProportionValue
{
    public static ProportionValue<T> Create<T>(double proportion, T value)
    {
        return new ProportionValue<T> { Proportion = proportion, Value = value };
    }

    static Random random = new Random();
    public static T ChooseByRandom<T>(
        this IEnumerable<ProportionValue<T>> collection)
    {
        var rnd = random.NextDouble();
        foreach (var item in collection)
        {
            if (rnd < item.Proportion)
                return item.Value;
            rnd -= item.Proportion;
        }
        throw new InvalidOperationException(
            "The proportions in the collection do not add up to 1.");
    }
}

用法：

var list = new[] {
    ProportionValue.Create(0.7, "a"),
    ProportionValue.Create(0.2, "b"),
    ProportionValue.Create(0.1, "c")
};

// Outputs "a" with probability 0.7, etc.
Console.WriteLine(list.ChooseByRandom());

这篇关于选择基于百分比加权的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！