根據r中其他列的字符串內容創建data.table列

Question

我正在使用與以下類似的數據進行工作/爭吵/詛咒：

names <- data.table(namesID = 1:3, fullName =  c("bob so", "larry po", "sam ho"))

trips <- data.table(tripsID = 1:3, tripNames= c("Mexico", "Alaska", "New Jersey"), 
                    tripMembers = c("bob so|larry po|sam ho","bob so|sam ho", "bob so|larry po")
                   ) 

我想創建一個這樣的新表，獲取tripMembers，並將正確的nameID連接到正確的tripID和tripName。 我想這是一個連接（嘗試了很多連接）？

namesTrips 
tripsID   tripNames          namesID
1         "Mexico"            1
1         "Mexico"            2
1         "Mexico"            3
2         "Alaska"            1
2         "Alaska"            3
3         "New Jersey"        1
3         "New Jersey"        2

Answer 1

你可以這樣做：

# split the tripMembers column and unnest it; then join with names on the tripMembers
namesTrips <- trips[, .(tripMembers = unlist(strsplit(tripMembers, "\\|"))), 
                      by = .(tripsID, tripNames)][names, on = .(tripMembers = fullName)]

namesTrips[, tripMembers := NULL][order(tripsID)]

#   tripsID  tripNames namesID
#1:       1     Mexico       1
#2:       1     Mexico       2
#3:       1     Mexico       3
#4:       2     Alaska       1
#5:       2     Alaska       3
#6:       3 New Jersey       1
#7:       3 New Jersey       2