R data.table roll =“最近".实际上不是最近的 [英] R data.table roll="nearest" not actually nearest
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问题描述
鉴于以下data.tables,我很惊讶地看到5.9索引与5而不是6匹配.
Given the following data.tables I'm surprised to see the 5.9 index matching with 5 rather than 6.
我不太了解发生了什么事.
I don't quite understand what's going on.
dat <- data.table(index = c(4.3, 5.9, 1.2), datval = runif(3)+10,
datstuff="test")
reference <- data.table(index = 1:10, refjunk = "junk", refval = runif(10))
dat[, dat_index := index]
reference[dat, roll="nearest", on="index"]
至少出于我最近的理解,我希望看到3行引用的index == 6行与dat的index == 5.9行匹配.
I would expect to see 3 rows with the index==6 row in reference being matched with the index==5.9 row in dat, at least for my understanding on nearest.
这是预期的行为吗?
使用R 3.3.2,data.table 1.10.4
Using R 3.3.2, data.table 1.10.4
推荐答案
因为 1:10
是整数的向量,所以对整数和 as.integer(5.9)的联接完成了
是5.
Because 1:10
is a vector of integers, the join in done on integers and as.integer(5.9)
is 5.
您可以使用 1:10 + 0
来构建数字:
You can, use 1:10+0
to build a numeric:
reference <- data.table(index = 1:10+0, ref_index=1:10, refjunk = "junk", refval = runif(10))
reference[dat, roll="nearest", on="index"]
index ref_index refjunk refval datval datstuff dat_index
1: 4.3 4 junk 0.09868848 10.37403 test 4.3
2: 5.9 6 junk 0.60545607 10.86906 test 5.9
3: 1.2 1 junk 0.50005336 10.07994 test 1.2
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