我试图在导入到R中的data.table对象中找到两个列表列之间的交集。我复制了下面的data.table，并使用完全相同的值：

DT_1 <- data.table(
  ego = as.integer(c(128320, 128320)),
  list_ego = list(as.integer(c(1,4)), as.integer(c(1,4))),
  alter = as.integer(c(48259, 167757)),
  list_alter = list(as.integer(c(4,3,1,5)), as.integer(c(3,1,4,5)))
)

然后我运行下面的代码并得到一条错误消息：

> DT_1[, shared_list := mapply(FUN = intersect, list_ego, list_alter)]
Error in `[.data.table`(DT_1, , `:=`(shared_list, mapply(FUN = intersect,  : 
  Supplied 4 items to be assigned to 2 items of column 'shared_list'. If you wish to 'recycle' the RHS please use rep() to make this intent clear to readers of your code.
In addition: Warning message:
In `[.data.table`(DT_1, , `:=`(shared_list, mapply(FUN = intersect,  :
  2 column matrix RHS of := will be treated as one vector

奇怪的是，当我使用其他值时，同样的代码也能工作：

> DF_2 <- data.table(
+   ego = as.integer(c(1, 1)),
+   list_ego = list(as.integer(c(100,200)), as.integer(c(100,200))),
+   alter = as.integer(c(2, 3)),
+   list_alter = list(as.integer(c(100, 300)), as.integer(c(200, 300)))
+ )
> DF_2[, shared_list := mapply(FUN = intersect, list_ego, list_alter)]
> DF_2
   ego list_ego alter list_alter shared_list
1:   1  100,200     2    100,300         100
2:   1  100,200     3    200,300         200

我需要让这段代码适用于所有值，因为我将在许多csv导入的data.table对象的循环中使用它。