说我有以下数据帧:
DF1 <- data.frame("A" = rep(c("A","B"), 18),
"B" = rep(c("C","D","E"), 12),
"NUM"= rep(rnorm(36,10,1)),
"TEST" = rep(NA,36))
DF2 <- data.frame("A" = rep("A",6),
"B" = rep(c("C","D"),6),
"VAL" = rep(c(1,3),3))
*注意:A
中变量B
和DF2
的每个唯一组合都应具有唯一VAL
。
对于每一行,如果NA
列中的值,我想将TEST
中的VAL
替换为DF1
中A
的相应值和A
匹配,B
和B
列中的值与该行匹配。否则,我将TEST
保留为NA
。如果不使用匹配来循环每个组合,我将如何做到这一点?
理想情况下,答案会缩放到两个数据框,其中有许多列要匹配。
答案 0 :(得分:8)
# this is your DF1
DF1 <- data.frame("A" = rep(c("A","B"), 18),
"B" = rep(c("C","D","E"), 12),
"NUM"= rep(rnorm(36,10,1)),
"TEST" = rep(NA,36))
#this is a DF2 i created, with unique A, B, VAL
DF2 <- data.frame("A" = rep(c("A","B"),3),
"B" = rep(c("C","D","E"),2),
"VAL" = rep(1:6))
# and this is the answer of what i assume you want
tmp <- merge(DF1,DF2, by=c("A","B"), all.x=TRUE, all.y=FALSE)
DF1[4] <- tmp[5]
答案 1 :(得分:6)
正如Akrun在评论中提到的,您的查找表(DF2)需要简化为其唯一的A / B组合。对于您当前的数据框架,这不是问题,但如果同一组合有多个可能的值,则需要其他规则。从那里,解决方案很简单:
DF2.u <- unique(DF2)
DF3 <- merge(DF1, DF2.u, all = T)
请注意,这将生成一个新的数据框,其中包含空TEST列(所有值NA
)和从DF2分配的VAL列。要做到你想要的(尽可能用VAL替换TEST),这里有一些稍微笨重的代码:
DF1$TEST <- merge(DF1, DF2.u, all = T)$VAL
编辑:在回答您的问题时,如果需要,您可以将DF2归结为非常简单:
DF2$C <- c(1:12) #now unique() won't work
DF2.u <- unique(DF2[1:3])
A B VAL
1 A C 1
2 A D 3