Question

我很想知道,如何用概率来产生愤怒的价值观。

As an example, I have four integers with their probability values: 1|0.4, 2|0.3, 3|0.2, 4|0.1

我怎么能考虑到这四个数字的概率,得出这些数字?

Answer 1

这里是一个有用的骗局:-

function randomWithProbability() {
  var notRandomNumbers = [1, 1, 1, 1, 2, 2, 2, 3, 3, 4];
  var idx = Math.floor(Math.random() * notRandomNumbers.length);
  return notRandomNumbers[idx];
}

Answer 2

A simple naive approach can be:

function getRandom(){
  var num=Math.random();
  if(num < 0.3) return 1;  //probability 0.3
  else if(num < 0.6) return 2; // probability 0.3
  else if(num < 0.9) return 3; //probability 0.3
  else return 4;  //probability 0.1
}

Answer 3

更灵活的解决方案,以@bhups回答为基础。这使用了各种概率值(重量)。重量应等于1。

var weights = [0.3, 0.3, 0.3, 0.1]; // probabilities
var results = [1, 2, 3, 4]; // values to return

function getRandom () {
    var num = Math.random(),
        s = 0,
        lastIndex = weights.length - 1;

    for (var i = 0; i < lastIndex; ++i) {
        s += weights[i];
        if (num < s) {
            return results[i];
        }
    }

    return results[lastIndex];
};

Answer 4

我建议对随机次数的概率和其余部分进行持续检查。

这项职能首先确定最后一项可能的指数的回报值,并在其他随机值低于实际概率之前重新计算。

可能性必须一概。

function getRandomIndexByProbability(probabilities) {
    var r = Math.random(),
        index = probabilities.length - 1;

    probabilities.some(function (probability, i) {
        if (r < probability) {
            index = i;
            return true;
        }
        r -= probability;
    });
    return index;
}

var i,
    probabilities = [0.4, 0.3, 0.2, 0.09, 0.01 ],
    count = {},
    index;

probabilities.forEach(function (a) { count[a] = 0; });

for (i = 0; i < 1e6; i++) {
    index = getRandomIndexByProbability(probabilities);
    count[probabilities[index]]++
}

console.log(count);

Answer 5

这是一种最灵活的解决办法,可以在任何具有概率的物体内选择:

// set of object with probabilities:
const set = {1:0.4,2:0.3,3:0.2,4:0.1};

// get probabilities sum:
var sum = 0;
for(let j in set){
    sum += set[j];
}

// choose random integers:
console.log(pick_random());

function pick_random(){
    var pick = Math.random()*sum;
    for(let j in set){
        pick -= set[j];
        if(pick <= 0){
            return j;
        }
    }
}

Answer 6

let cases = {
  10 : 60,// 0-10 : 60  => 10%
  90 : 10,// 10-90 : 10  => 80%
  100 : 70,// 90-100 : 70 => 10%
};
function randomInt(){
  let random = Math.floor(Math.random() * 100);
  for(let prob in cases){
    if(prob>=random){
      return cases[prob];
    }
  }
}
console.log(randomInt())

Answer 7

Rom098的答复有所改动,使之更加灵活。添加加权作为单位阵列。

function randomWithProbability(outcomes, weights){
    if(!weights){
        weights=Array(outcomes.length).fill(1);
    }
    let totalWeight=weights.reduce((prev, curr)=>prev+=curr);
    const num=Math.random();
    let sum=0, lastIndex=weights.length-1;
    for(let i=0; i<=lastIndex; i++){
        sum+=weights[i]/totalWeight;
        if(num<sum) return outcomes[i];
    }
    return outcomes[lastIndex];
}

for(let i=0; i<20; i++){
  console.log(randomWithProbability([true, false], [10,1]));
}

友情链接