Question

我有一个丑陋的列表和空数据框列表（api有趣！）。我想要的是name元素的向量。在这种情况下，向量的长度应为13，其中NA为data frame with 0 columns and 0 rows。

myList <- list(structure(list(uuid = "x1", 
    name = "thanks"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(uuid = "x2", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(), .Names = character(0), row.names = integer(0), class = "data.frame"), 
    structure(list(uuid = "x3", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(uuid = "x4", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(uuid = "x5", 
        name = "enrolled"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(uuid = "x6", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(), .Names = character(0), row.names = integer(0), class = "data.frame"), 
    structure(list(uuid = "x7", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(), .Names = character(0), row.names = integer(0), class = "data.frame"), 
    structure(list(uuid = "x8", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(uuid = "x9", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L), 
    structure(list(uuid = "x10", 
        name = "team"), .Names = c("uuid", "name"), class = "data.frame", row.names = 1L))

期望的输出：

"thanks" "team" NA "team" "team" "enrolled" "team" NA "team" NA "team" "team" "team"

Answer 1

也许它适合你：

sapply(myList, function(x){
    if(all(dim(x) == c(0,0))){
        x <- NA
    } else x <- x$name
})

从列表列表和空数据帧中提取元素

1 个答案: