考虑下面四个百分比,用浮点数表示:

    13.626332%
    47.989636%
     9.596008%
    28.788024%
   -----------
   100.000000%

我需要用整数表示这些百分比。如果我简单地使用Math.round(),我最终得到的总数是101%。

14 + 48 + 10 + 29 = 101

如果我使用parseInt(),我最终得到了97%。

13 + 47 + 9 + 28 = 97

有什么好的算法可以将任何百分比数表示为整数,同时还保持总数为100%?


编辑:在阅读了一些评论和回答后,显然有很多方法可以解决这个问题。

在我看来,为了保持数字的真实性,“正确”的结果是最小化总体误差的结果,定义为相对于实际值会引入多少误差舍入:

        value  rounded     error               decision
   ----------------------------------------------------
    13.626332       14      2.7%          round up (14)
    47.989636       48      0.0%          round up (48)
     9.596008       10      4.0%    don't round up  (9)
    28.788024       29      2.7%          round up (29)

在平局的情况下(3.33,3.33,3.33)可以做出任意的决定(例如3,4,3)。


当前回答

我认为以下几点可以达到你的目的

function func( orig, target ) {

    var i = orig.length, j = 0, total = 0, change, newVals = [], next, factor1, factor2, len = orig.length, marginOfErrors = [];

    // map original values to new array
    while( i-- ) {
        total += newVals[i] = Math.round( orig[i] );
    }

    change = total < target ? 1 : -1;

    while( total !== target ) {

        // Iterate through values and select the one that once changed will introduce
        // the least margin of error in terms of itself. e.g. Incrementing 10 by 1
        // would mean an error of 10% in relation to the value itself.
        for( i = 0; i < len; i++ ) {

            next = i === len - 1 ? 0 : i + 1;

            factor2 = errorFactor( orig[next], newVals[next] + change );
            factor1 = errorFactor( orig[i], newVals[i] + change );

            if(  factor1 > factor2 ) {
                j = next; 
            }
        }

        newVals[j] += change;
        total += change;
    }


    for( i = 0; i < len; i++ ) { marginOfErrors[i] = newVals[i] && Math.abs( orig[i] - newVals[i] ) / orig[i]; }

    // Math.round() causes some problems as it is difficult to know at the beginning
    // whether numbers should have been rounded up or down to reduce total margin of error. 
    // This section of code increments and decrements values by 1 to find the number
    // combination with least margin of error.
    for( i = 0; i < len; i++ ) {
        for( j = 0; j < len; j++ ) {
            if( j === i ) continue;

            var roundUpFactor = errorFactor( orig[i], newVals[i] + 1)  + errorFactor( orig[j], newVals[j] - 1 );
            var roundDownFactor = errorFactor( orig[i], newVals[i] - 1) + errorFactor( orig[j], newVals[j] + 1 );
            var sumMargin = marginOfErrors[i] + marginOfErrors[j];

            if( roundUpFactor < sumMargin) { 
                newVals[i] = newVals[i] + 1;
                newVals[j] = newVals[j] - 1;
                marginOfErrors[i] = newVals[i] && Math.abs( orig[i] - newVals[i] ) / orig[i];
                marginOfErrors[j] = newVals[j] && Math.abs( orig[j] - newVals[j] ) / orig[j];
            }

            if( roundDownFactor < sumMargin ) { 
                newVals[i] = newVals[i] - 1;
                newVals[j] = newVals[j] + 1;
                marginOfErrors[i] = newVals[i] && Math.abs( orig[i] - newVals[i] ) / orig[i];
                marginOfErrors[j] = newVals[j] && Math.abs( orig[j] - newVals[j] ) / orig[j];
            }

        }
    }

    function errorFactor( oldNum, newNum ) {
        return Math.abs( oldNum - newNum ) / oldNum;
    }

    return newVals;
}


func([16.666, 16.666, 16.666, 16.666, 16.666, 16.666], 100); // => [16, 16, 17, 17, 17, 17]
func([33.333, 33.333, 33.333], 100); // => [34, 33, 33]
func([33.3, 33.3, 33.3, 0.1], 100); // => [34, 33, 33, 0] 
func([13.25, 47.25, 11.25, 28.25], 100 ); // => [13, 48, 11, 28]
func( [25.5, 25.5, 25.5, 23.5], 100 ); // => [25, 25, 26, 24]

最后一件事,我使用问题中最初给出的数字运行函数,与期望的输出进行比较

func([13.626332, 47.989636, 9.596008, 28.788024], 100); // => [48, 29, 13, 10]

这与问题想要的不同=>[48,29,14,9]。我无法理解这一点,直到我看了总误差范围

-------------------------------------------------
| original  | question | % diff | mine | % diff |
-------------------------------------------------
| 13.626332 | 14       | 2.74%  | 13   | 4.5%   |
| 47.989636 | 48       | 0.02%  | 48   | 0.02%  |
| 9.596008  | 9        | 6.2%   | 10   | 4.2%   |
| 28.788024 | 29       | 0.7%   | 29   | 0.7%   |
-------------------------------------------------
| Totals    | 100      | 9.66%  | 100  | 9.43%  |
-------------------------------------------------

从本质上讲,我的函数的结果实际上引入了最少的误差。

小提琴在这里

其他回答

检查如果这是有效的或不就我的测试用例,我能够得到这个工作。

假设number是k;

按降序排序百分比。 从降序遍历每个百分比。 计算k的百分比第一个百分比采取数学。输出的天花板。 下一个k = k-1 遍历直到所有百分比被消耗。

下面是@varun-vohra答案的一个简单的Python实现:

def apportion_pcts(pcts, total):
    proportions = [total * (pct / 100) for pct in pcts]
    apportions = [math.floor(p) for p in proportions]
    remainder = total - sum(apportions)
    remainders = [(i, p - math.floor(p)) for (i, p) in enumerate(proportions)]
    remainders.sort(key=operator.itemgetter(1), reverse=True)
    for (i, _) in itertools.cycle(remainders):
        if remainder == 0:
            break
        else:
            apportions[i] += 1
            remainder -= 1
    return apportions

你需要math, itertools, operator。

我不确定你需要什么程度的精度,但我要做的就是简单地把前n个数字加1,n是小数总和的上界。在这种情况下,它是3,所以我将给前3项加1,然后将其余的取整。当然,这并不是非常准确,有些数字可能会四舍五入或在不应该的时候,但它工作得很好,总是会得到100%。

因此[13.626332,47.989636,9.596008,28.788024]将是[14,48,10,28],因为Math.ceil(.626332+.989636+.596008+.788024) == 3

function evenRound( arr ) {
  var decimal = -~arr.map(function( a ){ return a % 1 })
    .reduce(function( a,b ){ return a + b }); // Ceil of total sum of decimals
  for ( var i = 0; i < decimal; ++i ) {
    arr[ i ] = ++arr[ i ]; // compensate error by adding 1 the the first n items
  }
  return arr.map(function( a ){ return ~~a }); // floor all other numbers
}

var nums = evenRound( [ 13.626332, 47.989636, 9.596008, 28.788024 ] );
var total = nums.reduce(function( a,b ){ return a + b }); //=> 100

你总是可以告诉用户这些数字是四舍五入的,可能不是非常准确……

这是一个银行家四舍五入的例子,又名“四舍五入半偶数”。BigDecimal支持。它的目的是确保四舍五入平衡,即不偏袒银行或客户。

对于那些在熊猫系列中有百分比的人,这里是我的最大余数方法的实现(就像Varun Vohra的答案一样),在那里你甚至可以选择你想要四舍五入的小数。

import numpy as np

def largestRemainderMethod(pd_series, decimals=1):

    floor_series = ((10**decimals * pd_series).astype(np.int)).apply(np.floor)
    diff = 100 * (10**decimals) - floor_series.sum().astype(np.int)
    series_decimals = pd_series - floor_series / (10**decimals)
    series_sorted_by_decimals = series_decimals.sort_values(ascending=False)

    for i in range(0, len(series_sorted_by_decimals)):
        if i < diff:
            series_sorted_by_decimals.iloc[[i]] = 1
        else:
            series_sorted_by_decimals.iloc[[i]] = 0

    out_series = ((floor_series + series_sorted_by_decimals) / (10**decimals)).sort_values(ascending=False)

    return out_series