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

或者像这样简单,你只需要累积误差…

const p = [13.626332, 47.989636, 9.596008, 28.788024];
const round = (a, e = 0) => a.map(x => (r = Math.round(x + e), e += x - r, r));
console.log(round(p));

结果:[14,48,9,29]

其他回答

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。

不要把四舍五入的数字相加。你会得到不准确的结果。总数可能会显著偏离,这取决于术语的数量和小数部分的分布。

显示四舍五入的数字,但和实际值。根据你呈现数字的方式不同,实际的方法也会有所不同。这样你就能得到

14 48 10 29 __ 100

不管怎样,都会有差异。在你的例子中,没有办法显示加起来等于100的数字而不以错误的方式“舍入”一个值(最小的错误是将9.596更改为9)

EDIT

你需要在以下选项中做出选择:

项目的准确性 和的准确性(如果你是四舍五入的值) 四舍五入的项目与四舍五入的总和的一致性)

大多数情况下,当处理百分比时,第三种方法是最好的选择,因为当总数等于101%时比当单个项目的总数不等于100时更明显,并且您可以保持单个项目的准确性。“舍入”9.596到9在我看来是不准确的。

为了解释这一点,我有时会添加一个脚注,解释各个值是四舍五入的,可能不是100% -任何理解四舍五入的人都应该能够理解这个解释。

我用Javascript写了一个函数,它接受一个百分比数组,并使用最大余数方法输出一个四舍五入的百分比数组。它不使用任何库。

输入:[21.6,46.7,31,0.5,0.2]

输出:[22,47,31,0,0]

const values = [21.6, 46.7, 31, 0.5, 0.2]; console.log(roundPercentages(values)); function roundPercentages(values) { const flooredValues = values.map(e => Math.floor(e)); const remainders = values.map(e => e - Math.floor(e)); const totalRemainder = 100 - flooredValues.reduce((a, b) => a + b); // Deep copy because order of remainders is important [...remainders] // Sort from highest to lowest remainder .sort((a, b) => b - a) // Get the n largest remainder values, where n = totalRemainder .slice(0, totalRemainder) // Add 1 to the floored percentages with the highest remainder (divide the total remainder) .forEach(e => flooredValues[remainders.indexOf(e)] += 1); return flooredValues; }

或者像这样简单,你只需要累积误差…

const p = [13.626332, 47.989636, 9.596008, 28.788024];
const round = (a, e = 0) => a.map(x => (r = Math.round(x + e), e += x - r, r));
console.log(round(p));

结果:[14,48,9,29]

我已经实现了Varun Vohra的答案在这里的列表和字典的方法。

import math
import numbers
import operator
import itertools


def round_list_percentages(number_list):
    """
    Takes a list where all values are numbers that add up to 100,
    and rounds them off to integers while still retaining a sum of 100.

    A total value sum that rounds to 100.00 with two decimals is acceptable.
    This ensures that all input where the values are calculated with [fraction]/[total]
    and the sum of all fractions equal the total, should pass.
    """
    # Check input
    if not all(isinstance(i, numbers.Number) for i in number_list):
        raise ValueError('All values of the list must be a number')

    # Generate a key for each value
    key_generator = itertools.count()
    value_dict = {next(key_generator): value for value in number_list}
    return round_dictionary_percentages(value_dict).values()


def round_dictionary_percentages(dictionary):
    """
    Takes a dictionary where all values are numbers that add up to 100,
    and rounds them off to integers while still retaining a sum of 100.

    A total value sum that rounds to 100.00 with two decimals is acceptable.
    This ensures that all input where the values are calculated with [fraction]/[total]
    and the sum of all fractions equal the total, should pass.
    """
    # Check input
    # Only allow numbers
    if not all(isinstance(i, numbers.Number) for i in dictionary.values()):
        raise ValueError('All values of the dictionary must be a number')
    # Make sure the sum is close enough to 100
    # Round value_sum to 2 decimals to avoid floating point representation errors
    value_sum = round(sum(dictionary.values()), 2)
    if not value_sum == 100:
        raise ValueError('The sum of the values must be 100')

    # Initial floored results
    # Does not add up to 100, so we need to add something
    result = {key: int(math.floor(value)) for key, value in dictionary.items()}

    # Remainders for each key
    result_remainders = {key: value % 1 for key, value in dictionary.items()}
    # Keys sorted by remainder (biggest first)
    sorted_keys = [key for key, value in sorted(result_remainders.items(), key=operator.itemgetter(1), reverse=True)]

    # Otherwise add missing values up to 100
    # One cycle is enough, since flooring removes a max value of < 1 per item,
    # i.e. this loop should always break before going through the whole list
    for key in sorted_keys:
        if sum(result.values()) == 100:
            break
        result[key] += 1

    # Return
    return result