根据条件合并R中的数据表

Question

首先，我试图通过 R 的数据表库的文档找到解决方案，但没有帮助。我有两个数据数据表，它们具有关键的性别和权重。我如何将它们与条件t1$gender == t2$gender和t1$weight <= t2$weight合并t1$weight <= t2$weight ?

这是表格：

t1 <- data.table(ID = c(1:6), gender = c("m", "m", "m", "m", "f", "f"), w = c(1:3))

t2 <- data.table(gender = c("m", "f", NA), w = c(1, 2, 3), z = c(4, 2, 3))

Answer 1

我们可以使用非对等连接

library(data.table)
setDT(t1)[t2, .SD, on = .(gender, weight <= weight)]

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如果我们也对“z”列感兴趣

setDT(t1)[t2, c(.SD, .(z = z)), on = .(gender, w <= w), nomatch = FALSE]
#   ID gender w z
#1:  1      m 1 4
#2:  4      m 1 4
#3:  5      f 2 2