Python:如何在两个单独的数组之间找到两个相等/最接近的值? [英] Python: How to find two equal/closest values between two separate arrays?

问题描述

假设我们有两个长度相等的数组:

Let's say we have two arrays of equal length:

arr1 = (21, 2, 3, 5, 13)
arr2 = (10, 4.5, 9, 12, 20)

arr1 中的哪个变量与 arr2 中的变量等于/最接近?

Which variable from arr1 is equal / closest to a variable from arr2?

通过查看这两个列表，我们可以轻松地说出最接近的数字是 4.5 和 5 .我试图实现一个函数，该函数在给定两个列表的情况下返回两个最接近的值，对于上面的示例来说，它有点有效，但由于它不是最优的，所以几乎不是解决方案.而且，当我们对数组进行如下更改时，您可以轻松地检查该函数是否失败:

Looking at these two lists we can easily say that the closest numbers are 4.5 and 5. I've tried to implement a function that returns two closest values given two lists and it kinda works for the examples above, but it is barely a solution because it is not optimal. And you can easily check that the function fails when we slightly change the arrays like this:

arr1 = (21, 2, 3, 5, 13)
arr2 = (10, 4.5, 9, 12, 18)

函数返回的值为13和18

the values the function returns are 13 and 18

这是函数:

def get_nearest(arr1, arr2):
    lr = [[0, 0, 0]]
    for x1 in arr1:
        for x2 in arr2:
            r = (x1 / x2 % (x1 + x2))
            print x1, x2, r
            if r <= 1 and r >= lr[0][2]:
                lr.pop()
                lr.append([x1, x2, r])
    return lr

您能提出更好的选择吗?

Can you come up with a better one?

推荐答案

速度有问题吗?你在乎领带吗?如果没有，那像这样的简单东西怎么办

Is speed an issue? Do you care about ties? If not, what about something simple like

from itertools import product
sorted(product(arr1, arr2), key=lambda t: abs(t[0]-t[1]))[0]

两者都

arr1 = (21, 2, 3, 5, 13)
arr2 = (10, 4.5, 9, 12, 20)

和

arr1 = (21, 2, 3, 5, 13)
arr2 = (10, 4.5, 9, 12, 18)

这产生

(5, 4.5)

说明:

product(arr1, arr2) = [(a1, a2) for (a1, a2) in product(arr1, arr2)]

产生所有 N ** 2 对数字的列表:

yields a list of all N**2 pairs of numbers:

[(21, 10), (21, 4.5), ..., (13, 12), (13, 20)]

然后，我们使用 sorted 按绝对差( | a1-a2 | )对它们进行排序.通过传递 sorted 和 key 关键字，我们告诉 sorted 使用排序标准 lambda t:abs(t [0]-t[1]).绝对差最小的那对被放置在排序数组的第一个索引中，因此我们可以通过在末尾添加 [0] 来抓住它.

Then we sort them by the absolute difference (|a1 - a2|) using sorted. By passing sorted the key keyword, we tell sorted to use the sorting criteria lambda t: abs(t[0] - t[1]). The pair with the smallest absolute difference is placed in the first index of the sorted array, so we can grab it by tacking [0] on the end.

正如Piotr在评论中所建议的那样，您可以将 key = func 馈入 min 和 max ，从而大大加快了速度.尝试尝试:

As suggested by Piotr in the comments, you can feed a key=func to min and max, which speeds this up considerably. Try instead:

from itertools import product
min(product(arr1, arr2), key=lambda t: abs(t[0]-t[1]))[0]

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