[英]Is there an R function to merge two data frames based on two columns separately matching to the same column?
我想分別基於兩列之一( "VALA"
、 "VALB"
)填充兩個值( "VAL"
"VALB"
)。
# Data
DF1 <- data.frame("colA" = rep(c("A","B"), 6),
"colB" = rep(c("C","D","E"), 4))
DF2 <- data.frame("colC" = c("A","B","C","D","E"),
"VAL" = 1:5)
# three join calls
tmp1 <- left_join(DF1, DF2, by=c("colA"="colC"))
names(tmp1)[3] <- "VALA"
tmp2 <- left_join(DF1, DF2, by=c("colB"="colC"))
names(tmp2)[3] <- "VALB"
left_join(tmp1, tmp2, by=c("colA", "colB"))
# colA colB VALA VALB
# 1 A C 1 3
# 2 A C 1 3
# 3 B D 2 4
# 4 B D 2 4
# 5 A E 1 5
# 6 A E 1 5
# 7 B C 2 3
# 8 B C 2 3
# 9 A D 1 4
# 10 A D 1 4
# 11 B E 2 5
# 12 B E 2 5
# 13 A C 1 3
# 14 A C 1 3
# 15 B D 2 4
# 16 B D 2 4
# 17 A E 1 5
# 18 A E 1 5
# 19 B C 2 3
# 20 B C 2 3
# 21 A D 1 4
# 22 A D 1 4
# 23 B E 2 5
# 24 B E 2 5
為什么最后一個操作給出 24 行作為輸出而不是預期的 12 行?
有沒有可能以最優雅的方式(而不是 3 個連接操作)實現相同的預期?
您可以使用match
來查找相應的值並cbind
resluting 列。
cbind(DF1, VALA=DF2$VAL[match(DF1$colA, DF2$colC)],
VALB=DF2$VAL[match(DF1$colB, DF2$colC)])
colA colB VALA VALB
#1 A C 1 3
#2 B D 2 4
#3 A E 1 5
#4 B C 2 3
#5 A D 1 4
#6 B E 2 5
#7 A C 1 3
#8 B D 2 4
#9 A E 1 5
#10 B C 2 3
#11 A D 1 4
#12 B E 2 5
或使用名稱:
x <- setNames(DF2$VAL, DF2$colC)
cbind(DF1, VALA=x[DF1$colA], VALB=x[DF1$colB])
並且如果許多列在lapply
內使用match
cbind(DF1, setNames(lapply(DF1, function(x) DF2$VAL[match(x, DF2$colC)]),
sub("col", "VAL", names(DF1))))
# colA colB VALA VALB
#1 A C 1 3
#2 B D 2 4
#3 A E 1 5
#4 B C 2 3
#5 A D 1 4
#6 B E 2 5
#7 A C 1 3
#8 B D 2 4
#9 A E 1 5
#10 B C 2 3
#11 A D 1 4
#12 B E 2 5
嘗試使用%>%
一個接一個地組合left_join
並定義其后綴。
DF1 <- DF1 %>%
left_join(DF2, c("colA" = "colC")) %>%
left_join(DF2, c("colB" = "colC"),
suffix = c ("A", "B"))
> DF1
colA colB VALA VALB
1 A C 1 3
2 B D 2 4
3 A E 1 5
4 B C 2 3
5 A D 1 4
6 B E 2 5
7 A C 1 3
8 B D 2 4
9 A E 1 5
10 B C 2 3
11 A D 1 4
12 B E 2 5
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