如何在R中创建字符串组合答案

【问题标题】：How to create combination of strings in R如何在R中创建字符串组合
【发布时间】：2021-12-16 00:56:35
【问题描述】：

我有以下字符串：

center <- "XXXXXXX"
sides <- c("aa", "bb", "cc") # Could be longer than 3 members
# string length of members could be varied.

我想要做的是将sides 的成员附加到center 两端的字符串列表所有可能的组合，产生：

aaXXXXXXXaa
aaXXXXXXXbb
aaXXXXXXXcc

bbXXXXXXXbb
bbXXXXXXXaa
bbXXXXXXXcc

ccXXXXXXXcc
ccXXXXXXXaa
ccXXXXXXXbb

如何使用 R 实现这一目标？

【问题讨论】：

标签： r string vector combinations

【解决方案1】：

将expand.grid 和apply 与paste 一起使用：

> apply(expand.grid(sides, sides), 1, paste, collapse = center)
[1] "aaXXXXXXXaa" "bbXXXXXXXaa" "ccXXXXXXXaa" "aaXXXXXXXbb" "bbXXXXXXXbb" "ccXXXXXXXbb" "aaXXXXXXXcc" "bbXXXXXXXcc" "ccXXXXXXXcc"
>

或者：

>  apply(expand.grid(sides, center, sides), 1, paste, collapse='')
[1] "aaXXXXXXXaa" "bbXXXXXXXaa" "ccXXXXXXXaa" "aaXXXXXXXbb" "bbXXXXXXXbb" "ccXXXXXXXbb" "aaXXXXXXXcc" "bbXXXXXXXcc" "ccXXXXXXXcc"
>

或者正如@Wimpel 提到的，您可以使用data.table::CJ 来获取组合：

> apply(data.table::CJ(sides, sides), 1, paste0, collapse = center)
[1] "aaXXXXXXXaa" "aaXXXXXXXbb" "aaXXXXXXXcc" "bbXXXXXXXaa" "bbXXXXXXXbb" "bbXXXXXXXcc" "ccXXXXXXXaa" "ccXXXXXXXbb" "ccXXXXXXXcc"
>

【讨论】：

【解决方案2】：

试试

> do.call(paste0, expand.grid(sides, center, sides))
[1] "aaXXXXXXXaa" "bbXXXXXXXaa" "ccXXXXXXXaa" "aaXXXXXXXbb" "bbXXXXXXXbb"
[6] "ccXXXXXXXbb" "aaXXXXXXXcc" "bbXXXXXXXcc" "ccXXXXXXXcc"

【讨论】：