java map 递归_使用purrr :: map进行递归函数调用
我有一个数据框中的列表，我想使用 purrr::map() 测试是否有任何 NULL 元素，然后摆脱它们 .
虽然我能够使用sapply来做到这一点，但是 Map 不起作用 . 我读了https://cran.r-project.org/web/packages/purrr/purrr.pdf，但我可以't figure out what'我错过了 .
这是我的sapply代码 - 这很好用：
P_Trans
这是我为 purrr::map 尝试的一些事情，但它们不起作用 .
以下是我尝试过的四件事：
一个)
P_Trans %>% purrr::map(.,~is.null(Group))
b)
P_Trans %>% purrr::map(.,~is.null(.$Group))
C)
P_Trans %>% purrr::map(~is.null(.$Group))
d)
P_Trans %>% purrr::map(~is.null(Group))
有人可以纠正我的错误，让我知道我在做什么，我做错了以上四个选项？
数据：
dput(P_Trans)
structure(list(TransactionID = c("a1", "a1", "a1", "a2", "a2",
"a2", "a3", "a3", "a3", "a3", "a4", "a5", "a5", "a5", "a5", "a5",
"a6", "a6", "a7"), ProductID = c("A", "B", "1", "C", "4", "5",
"D", "C", "7", "8", "H", "1", "2", "3", "3", "1", "H", "15",
"22"), ProductType = c(1, 1, 2, 1, 2, 2, 1, 1, 2, 2, 1, 2, 2,
2, 2, 2, 1, 2, 3), Group = list(structure(list(Group = "Group1"), .Names = "Group", row.names = c(NA,
-1L), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = c("Group2", "Group3")), .Names = "Group", row.names = c(NA,
-2L), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group2"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group2"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group3"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = c("Group2", "Group3")), .Names = "Group", row.names = c(NA,
-2L), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group3"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group3"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group5"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group1"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group5"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), structure(list(
Group = "Group5"), .Names = "Group", row.names = c(NA, -1L
), class = c("tbl_df", "tbl", "data.frame")), NULL)), class = c("tbl_df",
"tbl", "data.frame"), row.names = c(NA, -19L), .Names = c("TransactionID",
"ProductID", "ProductType", "Group"))