在data.table中与范围之间 [英] between vs inrange in data.table

问题描述

在R的 data.table 中，何时应该在％between％和之间进行选择％inrange％用于子集操作？我已经阅读了之间的帮助页面？，但我仍在摸索差异。

In R's data.table, when should one choose between %between% and %inrange% for subsetting operations? I've read the help page for ?between and I'm still scratching my head as to the differences.

library(data.table)
X = data.table(a=1:5, b=6:10, c=c(5:1))


> X[b %between% c(7,9)]
   a b c
1: 2 7 4
2: 3 8 3
3: 4 9 2
> X[b %inrange% c(7,9)]
   a b c
1: 2 7 4
2: 3 8 3
3: 4 9 2

在我看来，它们看起来一样。

They look the same to me. Could someone please explain why there exist both operations?

推荐答案

> X
   a  b c
1: 1  6 5
2: 2  7 4
3: 3  8 3
4: 4  9 2
5: 5 10 1

使用注释中的示例：

> X[a %between% list(c, b)]
   a  b c
1: 3  8 3
2: 4  9 2
3: 5 10 1
> X[a %inrange% list(c, b)]
   a  b c
1: 1  6 5
2: 2  7 4
3: 3  8 3
4: 4  9 2
5: 5 10 1

似乎在之间单独查看每一行，并检查a中的值是否使该行的c< = a< = b。

It seems between looks at each row individually and checks to see if the value in a is such that c <= a <= b for that row.

inrange 寻找 c 中最小的标量值，例如 cmin 和 b 中的最大标量值， bmax ，形成范围 [cmin ，bmax] ，然后检查 a 是否在此范围 [cmin，bmax] ，对于 a 列中的每一行。

inrange looks for the smallest scalar value in c, say cmin and the largest scalar value in b, bmax, forming a range [cmin, bmax], and then checks to see if a lies in this range [cmin, bmax], for each row in the a column.

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