按相应子列表的长度对嵌套列表进行排序 [英] Sort a nested list by the length of the respective sublists

问题描述

如何按子列表的长度对嵌套列表进行排序:

How can I sort a nested list by the length of the sublists:

l <- list(list("a","b","c"), list("d","e"), list("f"))

使用它应该返回:

list(list("f"), list("d","e"), list("a","b","c"))

推荐答案

我会用过

l[order(sapply(l, length))]

@Arun的评论中给出的解决方案

The solution given in the comment of @Arun

l[order(vapply(l, length, 1L))]

通过告诉R长度函数返回的所有内容都是整数，可以提供一些性能优势:对于vapply，您基本上给R给出了函数将返回哪种类型的示例，这可以节省返回的强制时间值以适合单个原子向量."参见:

may give some performance advantage by telling R that everything returned by the length function will be an integer: "For vapply, you basically give R an example of what sort of thing your function will return, which can save some time coercing returned values to fit in a single atomic vector." See:

R分组功能:sapply vs. lapply vs. apply. vs. tapply vs. by vs.聚合

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