清理嵌套列表答案

【问题标题】：Clean a nested list清理嵌套列表
【发布时间】：2021-07-09 22:47:03
【问题描述】：

我有一个日期列表

d = list(list(structure(c(18292, 18321, 18352, 18382, 18413, 18443, 
18474, 18505, 18535, 18566, 18596, 18627), class = "Date")), 
    list(structure(c(18658, 18686, 18717, 18747, 18778, 18808, 
    18839, 18870, 18900, 18931, 18961, 18992), class = "Date")

列表里面访问列表的方法是做


d[[1]][[1]]

我想操作列表，这样我只需要执行 d[[1]] 即可访问第一个元素。但是，当我尝试取消列出时，它变成了

> unlist(d)
 [1] 18292 18321 18352 18382 18413 18443 18474 18505 18535 18566 18596 18627 18658 18686 18717 18747 18778 18808 18839 18870 18900
[22] 18931 18961 18992

为什么日期会变成数字？

【问题讨论】：

标签： r

【解决方案1】：

你应该设置recursive = FALSE

> unlist(d, recursive = FALSE)[[1]]
 [1] "2020-01-31" "2020-02-29" "2020-03-31" "2020-04-30" "2020-05-31"
 [6] "2020-06-30" "2020-07-31" "2020-08-31" "2020-09-30" "2020-10-31"
[11] "2020-11-30" "2020-12-31"

【讨论】：

【解决方案2】：

你可以使用purrr::flatten -

l <- purrr::flatten(d)
l

#[[1]]
# [1] "2020-01-31" "2020-02-29" "2020-03-31" "2020-04-30" "2020-05-31" "2020-06-30"
# [7] "2020-07-31" "2020-08-31" "2020-09-30" "2020-10-31" "2020-11-30" "2020-12-31"

#[[2]]
# [1] "2021-01-31" "2021-02-28" "2021-03-31" "2021-04-30" "2021-05-31" "2021-06-30"
# [7] "2021-07-31" "2021-08-31" "2021-09-30" "2021-10-31" "2021-11-30" "2021-12-31"

l[[1]]

# [1] "2020-01-31" "2020-02-29" "2020-03-31" "2020-04-30" "2020-05-31" "2020-06-30"
# [7] "2020-07-31" "2020-08-31" "2020-09-30" "2020-10-31" "2020-11-30" "2020-12-31"

【讨论】：

【解决方案3】：

我们可以在base R中使用do.call

do.call(c, lapply(d, `[[`, 1))`

【讨论】：