R的data.table中是否有“inter-record”函数？

我有以下数据表：

AssetNumber StartDate   ActionNumber    PerviousActionNumber
1       20090602    1   
1       20090626    3           
1       20090721    5           
1       20091008    1           
2       20090604    3           
2       20090628    2           
2       20090723    1           
2       20091010    2           
2       20091018    3           

使用以下内容加载数据集：

set <- structure(list(AssetNumber = c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L), 
    StartDate = c(20090602L, 20090626L, 20090721L, 20091008L, 
    20090604L, 20090628L, 20090723L, 20091010L, 20091018L), ActionNumber = c(1L, 
    3L, 5L, 1L, 3L, 2L, 1L, 2L, 3L), PerviousAction. = c(NA, 
    NA, NA, NA, NA, NA, NA, NA, NA)), .Names = c("AssetNumber", "StartDate", 
"ActionNumber", "PerviousActionNumber"), class = "data.frame", row.names = c(NA, 
-9L))

---

更一般地说，R中是否有一个特定的包包含这样的记录间函数？

您正在使用：=，通过引用查找赋值。这是相当基本的。我建议您阅读data.table手册/文档

# thanks to @agstudy
dt[, previousActionNumber := c(NA, head(ActionNumber, -1))]

# thanks to @agstudy
dt[, previousActionNumber := c(NA, head(ActionNumber, -1))]