如何在JavaScript中对数组进行统计分类？

Question

我在数组中有一堆数字，我需要对它们进行一些统计。 我需要知道数组中每个数字有多少个。

这是数组：

myArray =
[2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 17, 17, 17, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 25, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 27, 27, 28, 30, 30, 31, 31, 31, 31, 31, 31, 31, 31, 32, 32, 32, 32, 32, 32, 32, 33, 33, 33, 33, 33, 33, 34, 34, 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36, 37, 37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 40, 40, 40, 41, 41, 42, 42, 42, 42, 42, 42, 43, 43, 43, 44, 44, 44, 44, 44, 45, 45, 46, 46, 46, 46, 46, 46, 46, 47, 47, 47, 47, 47, 47, 48, 48, 48, 49, 49, 49, 49, 49, 49, 49, 49, 49, 50, 50, 50, 50, 50, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 52, 52, 53, 53, 53, 53, 53, 53, 53, 54, 54, 54, 55, 55, 55, 55, 55, 56, 57, 57, 57, 57, 57, 57, 57, 58, 59, 59, 59, 59, 59, 60, 60, 60, 60, 60, 61, 61, 62, 62, 63, 63, 63, 64, 64, 64, 64, 64, 65, 65, 66, 66, 66, 67, 67, 67, 68, 68, 68, 69, 69, 69, 69, 69, 69, 70, 70, 71, 71, 71, 71, 71, 71, 71, 72, 73, 73, 73, 73, 74, 74, 74, 75, 75, 75, 76, 77, 78, 78, 79, 79, 80, 80, 81, 81, 81, 81, 81, 82, 82, 82, 82, 83, 83, 83, 83, 84, 84, 84, 85, 85, 85, 85, 85, 86, 86, 86, 86, 86, 86, 87, 87, 87, 88, 88, 89, 89, 90, 90, 91, 91, 91, 92, 93, 94, 95, 95, 95, 95, 95, 96, 96, 96, 96, 97, 97, 99, 99, 99, 99, 99, 101, 101, 102, 102, 103, 103, 105, 105, 105, 106, 107, 107, 108, 108, 109, 109, 109, 109, 110, 112, 112, 113, 113, 113, 114, 114, 115, 116, 116, 117, 118, 120, 121, 121, 121, 122, 122, 123, 123, 123, 124, 124, 124, 124, 125, 126, 127, 128, 129, 130, 130, 131, 131, 131, 131, 132, 133, 133, 134, 134, 134, 136, 136, 136, 136, 137, 137, 137, 138, 138, 138, 139, 139, 139, 140, 141, 141, 142, 142, 143, 144, 144, 144, 144, 145, 150, 150, 153, 155, 159, 160, 160, 161, 162, 164, 164, 166, 176, 180, 180, 180, 181, 181, 187, 191, 192, 193, 194, 197, 200, 203, 211, 216, 224, 251, 280, 333]

这是我目前用来解析它的内容（效果不佳）：

    for (var key in myArray){
        var obj = myArray[key];

        var count = 0;
        while(obj < 30){
            myArrayStats[0] = count;
            obj++;
        }
        while(obj > 30 && obj < 40){
            myArrayStats[1] = count;
            obj++;
        }
        //etc....
    }

使用对象文字创建一个新数组会更好，更容易使用，但是我不确定该怎么做。

Answer 1

无论您是否对数组进行排序，这都行得通，但是它不应该比任何利用了无论如何都要对数组进行排序的算法都要慢得多：

var myArrayStats = [];
for(var i = myArray.length; i--;)
    myArrayStats[myArray[i]] = (myArrayStats[myArray[i]] || 0) + 1;

console.log(myArrayStats[6]);  // Outputs 7
console.log(myArrayStats[10]); // Outputs 5
console.log(myArrayStats[20]); // Outputs 5

如果只想对原始数组的一部分执行此操作，而不是使用slice（）获取所需的数组部分，然后对该数组执行与上述相同的操作：

var mySubArray = myArray.slice(0,30);
var myArrayStats = [];
for(var i = mySubArray.length; i--;)
    myArrayStats[mySubArray[i]] = (myArrayStats[mySubArray[i]] || 0) + 1;

console.log(myArrayStats[6]);  // Outputs 7
console.log(myArrayStats[9]);  // Outputs 7
console.log(myArrayStats[10]); // Outputs undefined

Answer 2

 myArray = [2, 3, 3, 3, 4, 4, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 14, 14] for (var a = myArray, b = {}, i = 0; i < myArray.length; i++) b[a[i]] ? b[a[i]]++ : b[a[i]] = 1; console.log(JSON.stringify(Object.keys(b) .map(function(c) { return [c, b[c]] }))); 

Answer 3

听起来好像您有相等间隔的bin，并希望计算每个中有多少个值。 由于这个问题是用jQuery标记的，因此我们从中使用实用程序函数来避免显式循环以显示另一种处理方法。 （我想PaulPRO的方法虽然更好。）

function hist(values, min, max, numBins) {
    var bins = [];
    var range = max - min;
    jQuery.each(values, function(i, value) {
        var bin = Math.floor(numBins * (value - min) / range);
        bin = Math.min(Math.max(bin, -1), numBins) + 1;
        bins[bin] = (bins[bin] || 0) + 1;
    });
    return bins;
}

我们可以使用以下代码来执行上面的代码：

function consoleHist(values, min, max, numBins) {
    var bins = hist(values, min, max, numBins);
    var step = (max - min) / numBins;
    jQuery.each(bins, function(i, count) {
        var lower = (i - 1) * step + min;
        var upper = lower + step;
        if (lower < min) {
            lower = -Infinity;
        }
        if (upper > max) {
            upper = Infinity;
        }
        console.log('[' + lower + ', ' + upper + '): ' + (count || 0));
    });
}

consoleHist([-10, 0, 11, 29, 30, 59, 60, 1000], 0, 60, 2);

在控制台上产生以下输出：

[-Infinity, 0): 1
[0, 30): 3
[30, 60): 2
[60, Infinity): 2