R：传播向量的有效方法答案

【问题标题】：R: Efficient way for spreading vectorsR：传播向量的有效方法
【发布时间】：2018-05-25 22:01:50
【问题描述】：

有没有一种高效的编程方法来解决以下任务？

想象以下向量：

A<-[a,b,c...k]

并希望通过以下方式传播它：让我们从例如开始n=2

B<-[a,a,b,b,c...,k,k]

现在 n=4 或任何大于 1 的数字

C<-[a,a,a,a,b,...,k,k,k,k]

通过循环来解决它似乎很容易，但是有没有我错过/可以使用的任何基于函数或向量的操作？一个 tidyverse 解决方案（用于在管道中使用它）对我来说是最好的解决方案。

（很难对这项任务进行研究，因为我是 R 的新手，并且没有正确的术语来搜索。任何帮助都会有所帮助。）

【问题讨论】：

标签： r function vector tidyverse

【解决方案1】：

让

A <- letters[1:11]
A
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k"

如果你使用函数rep 和参数each，你会得到你想要的：

rep(A, each=2)
 [1] "a" "a" "b" "b" "c" "c" "d" "d" "e" "e" "f" "f" "g" "g" "h" "h" "i" "i" "j"
[20] "j" "k" "k"

rep(A, each=3)
[1] "a" "a" "a" "b" "b" "b" "c" "c" "c" "d" "d" "d" "e" "e" "e" "f" "f" "f" "g"
[20] "g" "g" "h" "h" "h" "i" "i" "i" "j" "j" "j" "k" "k" "k"

【讨论】：

【解决方案2】：

一个选项是使用rep 和参数times = 2 或4，然后使用sort 结果。另一种选择是使用mapply，然后使用c 运算符。

 c(mapply(rep, 2 ,A)) # OR sort(rep(A, times = 2))
 #[1] "a" "a" "b" "b" "c" "c" "d" "d" "e" "e" "f" "f" "g" "g" "h" "h" "i" "i" "j" "j"
 #[21] "k" "k"

 c(mapply(rep,A, 4))  #OR sort(rep(A, times = 2))
 #[1] "a" "a" "a" "a" "b" "b" "b" "b" "c" "c" "c" "c" "d" "d" "d" "d" "e" "e" "e" "e"
 #[21] "f" "f" "f" "f" "g" "g" "g" "g" "h" "h" "h" "h" "i" "i" "i" "i" "j" "j" "j" "j"
 #[41] "k" "k" "k" "k"

【讨论】：