列字符串的唯一組合的子集

Question

在較大數據集的最后日期，我有關於表現最佳的數據。 接下來，我想對整個數據集進行子集化，以檢索那些表現最好的數據。 “最佳表演者”是兩個字符串的組合。 但是，到目前為止，我還不能正確地對數據進行子集化。

我嘗試使用％in％來完成部分工作，但它包括具有一個或另一個字符串變量的所有行，而不是兩者的唯一組合。

library(data.table)
best = data.table(Date = as.Date(c("2016-01-01", "2016-01-01")), x = c("a", "b"), y = c("p", "q"))
wholedt = data.table(Date = as.Date(c("2015-12-01","2015-12-01","2015-12-01","2016-01-01", "2016-01-01", "2016-01-01")), x = c("a", "c", "b", "a","a", "b"), y = c("p", "q", "q", "q","p", "q"))
SDbest_of_whole = wholedt[with(wholedt, x %in% best$x & y %in% best$y)]

預期輸出將包括（a，p）和（b，q）組合的所有數據點。 沒有（a，q）或（b，p）的組合

expected_output = data.table(Date = as.Date(c("2015-12-01","2015-12-01","2016-01-01", "2016-01-01")), x = c("a", "b","a", "b"), y = c("p", "q","p", "q"))
> expected_output
     Date x y
1: 2015-12-01 a p
2: 2015-12-01 b q
3: 2016-01-01 a p
4: 2016-01-01 b q

Answer 1

確保僅使用感興趣的組合的一種方法是merge數據集：

library(data.table)
best = data.table(Date = as.Date(c("2016-01-01", "2016-01-01")), x = c("a", "b"), y = c("p", "q"))
wholedt = data.table(Date = as.Date(c("2015-12-01","2015-12-01","2015-12-01","2016-01-01", "2016-01-01", "2016-01-01")), x = c("a", "c", "b", "a","a", "b"), y = c("p", "q", "q", "q","p", "q"))

best[,Date:=NULL]
merge(best, wholedt)

#    x y       Date
# 1: a p 2015-12-01
# 2: a p 2016-01-01
# 3: b q 2015-12-01
# 4: b q 2016-01-01

Answer 2

對於wholedt每一行，您要比較是否有best行是相同的。

SDbest_of_whole <- wholedt[apply(wholedt[,c('x', 'y')], 1, function(w) any(apply(best[,c('x', 'y')], 1, identical, w))),]