尝试将列表存储在长度为1的data.table中时出错 [英] Error when trying to store list in data.table of length 1

问题描述

尝试将向量存储在data.table中时，仅当data.table的长度大于1时，此方法才有效.

When trying to store a vector in a data.table, this works only when the data.table has length of more than one.

请在下面找到问题的简化版本

Please find below a simplified version of the problem

库(data.table)

dt <- data.table( a = c("a", "b"), l = list())
dt$l[[1]] <- c(1:3) 

结果:

   a     l
1: a 1,2,3
2: b

产生错误

dt <- data.table( a = c("a"), l = list())
dt$l[[1]] <- c(1:3) 

[<-.data.table(x，j =名称，值=值)中的错误:提供了3个项目，将它们分配给列"l"的1个项目.RHS长度必须为1(可以使用单个值)或与LHS长度完全匹配.如果您想回收" RHS，请显式使用rep()来使您的代码读者清楚这一意图.

Error in [<-.data.table(x, j = name, value = value) : Supplied 3 items to be assigned to 1 items of column 'l'. The RHS length must either be 1 (single values are ok) or match the LHS length exactly. If you wish to 'recycle' the RHS please use rep() explicitly to make this intent clear to readers of your code.

预期结果:

   a     l
1: a 1,2,3

推荐答案

这是您要找的东西吗?

dt <- data.table(a = "a", l = list())
dt[1L, l := list(list((1:3)))]

结果:

   a     l
1: a 1,2,3

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