R:找到最近的索引 [英] R: find nearest index

问题描述

我有两个具有几千个点的向量，但是在这里概括如下:

I have two vectors with a few thousand points, but generalized here:

A <- c(10, 20, 30, 40, 50)
b <- c(13, 17, 20)

如何获得最近到b的A标记?预期的结果将是c(1, 2, 2).

How can I get the indicies of A that are nearest to b? The expected outcome would be c(1, 2, 2).

我知道findInterval只能找到第一个出现的位置，而不能找到最近的出现，而且我知道which.min(abs(b[2] - A))的温度正在升高，但是我不知道如何将其向量化以用于长向量A和b.

I know that findInterval can only find the first occurrence, and not the nearest, and I'm aware that which.min(abs(b[2] - A)) is getting warmer, but I can't figure out how to vectorize it to work with long vectors of both A and b.

推荐答案

您可以将代码放在一个小应用程序中.我认为它的速度与for循环的速度相同，因此在技术上没有向量化:

You can just put your code in a sapply. I think this has the same speed as a for loop so isn't technically vectorized though:

sapply(b,function(x)which.min(abs(x - A)))

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