首先,让我们从DataTable 1 (DF1)开始:
date id sales cost city name
1: 06/19/2016 1 149 101 MTL Bank1
2: 06/20/2016 1 150 102 MTL Bank1
3: 06/21/2016 1 151 104 MTL Bank1
4: 06/22/2016 1 152 107 MTL Bank1
5: 06/23/2016 1 155 99 MTL Bank1
6: 06/19/2016 2 84 55 NY Bank2
7: 06/20/2016 2 83 55 NY Bank2
8: 06/21/2016 2 80 56 NY Bank2
9: 06/22/2016 2 81 57 NY Bank2
10: 06/23/2016 2 97 58 NY Bank2
library(data.table)
DF1 <- data.table(c("06/19/2016", "06/20/2016", "06/21/2016", "06/22/2016",
"06/23/2016", "06/19/2016", "06/20/2016", "06/21/2016",
"06/22/2016", "06/23/2016"),
c(1, 1, 1, 1, 1, 2, 2, 2, 2, 2),
c(149, 150, 151, 152, 155, 84, 83, 80, 81, 97),
c(101, 102, 104, 107, 99, 55, 55, 56, 57, 58),
c("MTL", "MTL", "MTL", "MTL", "MTL", "NY", "NY",
"NY", "NY", "NY"))
colnames(DF1) <- c("date", "id", "sales", "cost", "city")
我希望您能够使用查找表添加上面显示的
名称
列,格式如下:
id name start_date end_date status
1: 1 Bank1 06/19/2016 06/25/2016 0
2: 2 Bank2 06/27/2016 06/27/2017 0
3: 3 Bank3 06/22/2016 06/24/2017 1
4: 4 Bank3 06/23/2016 12/23/2016 1
lookup <- data.table(c(1, 2, 3, 4),
c("Bank1", "Bank2", "Bank3", "Bank3"),
c("06/19/2016", "06/27/2016", "06/22/2016", "06/23/2016"),
c("06/25/2016", "06/27/2017", "06/24/2017", "12/23/2016"),
c("0", "0", "1", "1"))
colnames(lookup) <- c("id", "name", "start_date", "end_date", "status")
在这种情况下,我会使用id来查找名称。当我尝试使用
merge
时,在DF1中总是有包含NA的新行。
setnames
来通过引用添加名称。 - FrankDF1[lookup, on="id", name := i.name]
。 - Frankx[i, on=, j]
时,这是一种特殊的语法,可以在键值参数j
下找到相关文档。此外还有一个x.
前缀。在这种情况下,它非常有用,可以确保我们从i=lookup
而不是已经存在于x=DF1
中的预先存在的列name
中提取列。关于这种语法如何有用的更多信息,请参见:https://dev59.com/tlQJ5IYBdhLWcg3wNjK4 - Frank