如何从列表列表中提取元素 [英] How to extract elements from list of lists

问题描述

我是 R 的新手.我在 R 中有一个列表 t1 看起来像

I am a newbie to R. I have a list t1 in R which looks like

[[1]]
[[1]][[1]]
[1] "a"       "control"


[[2]]
[[2]][[1]]
[1] "a"        "disease1"


[[3]]
[[3]][[1]]
[1] "a"        "disease2"


[[4]]
[[4]][[1]]
[1] "b"       "control"


[[5]]
[[5]][[1]]
[1] "b"        "disease1"


[[6]]
[[6]][[1]]
[1] "b"        "disease2"

我需要将第一个元素的唯一列表放入向量中，即 ["a", "b"] 来自该向量 t1.我怎样才能做到这一点?

I need to get a unique list of first elements into a vector i.e ["a", "b"] from this vector t1. How can I do this?

推荐答案

rapply 提供了另一种选择:

unique(rapply(t1, function(x) head(x, 1)))

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