在data.table
FAQ中,nomatch = NA
参数被认为与外连接类似。但是,我一直无法获得data.table
做一个完整的外连接 - 只有正确的外连接。如何使用data.table完成全连接?
例如:
a <- data.table("dog" = c(8:12), "cat" = c(15:19))
dog cat
1: 8 15
2: 9 16
3: 10 17
4: 11 18
5: 12 19
b <- data.table("dog" = 1:10, "bullfrog" = 11:20)
dog bullfrog
1: 1 11
2: 2 12
3: 3 13
4: 4 14
5: 5 15
6: 6 16
7: 7 17
8: 8 18
9: 9 19
10: 10 20
setkey(a, dog)
setkey(b, dog)
a[b, nomatch = NA]
dog cat bullfrog
1: 1 NA 11
2: 2 NA 12
3: 3 NA 13
4: 4 NA 14
5: 5 NA 15
6: 6 NA 16
7: 7 NA 17
8: 8 15 18
9: 9 16 19
10: 10 17 20
所以,nomatch = NA
产生右外连接(这是默认值)。如果我需要全面加入,该怎么办?例如:
merge(a, b, by = "dog", all = TRUE)
# Or with plyr:
join(a, b, by = "dog", type = "full")
dog cat bullfrog
1: 1 NA 11
2: 2 NA 12
3: 3 NA 13
4: 4 NA 14
5: 5 NA 15
6: 6 NA 16
7: 7 NA 17
8: 8 15 18
9: 9 16 19
10: 10 17 20
11: 11 18 NA
12: 12 19 NA
这可能与data.table
?
对于加入与data.table看到[此帖]最后的答案[1 ] [1]:http://stackoverflow.com/questions/14076065/data-table-inner-outer-join-with-na-in-join-column-of-type-double-bug ?rq = 1 – statquant 2013-03-03 22:45:58
对于与data.table加入各种见[此帖]最后的答案[1] [1]:http://stackoverflow.com/questions/14076065/data-table-inner-outer -a-in-join-column-of-type-double-bug?rq = 1 – statquant 2013-03-03 22:48:00