列中唯一值的总和

我想在满足某些条件后,每年在列中获得唯一值的总和。

以下是我从DPUT获得的数据:

structure(list(key = structure(c(1L, 1L, 4L, 2L, 3L, 4L, 2L, 
3L, 5L, 5L, 8L, 6L, 7L, 8L, 6L, 7L), .Label = c("1992_10_18_0", 
"1992_10_18_12", "1992_10_18_18", "1992_10_18_6", "1993_10_18_0", 
"1993_10_18_12", "1993_10_18_18", "1993_10_18_6"), class = "factor"), 
 RR = c(43.25, 43.25, 43.25, 43.25, 43.25, 43.25, 43.25, 43.25, 
 43.25, 43.25, 43.25, 43.25, 43.25, 43.25, 43.25, 43.25), 
 dist = c(1000.23361607017, 694.022935174544, 748.618896699399, 
 812.290633745208, 869.896619169459, 1136.88564181537, 
 1058.59136791648, 
 975.756885299645, 1000.23361607017, 694.022935174544, 
 748.618896699399, 
 812.290633745208, 869.896619169459, 1136.88564181537, 
 1058.59136791648, 
 975.756885299645), Year = c(1992L, 1992L, 1992L, 1992L, 1992L, 
 1992L, 1992L, 1992L, 1993L, 1993L, 1993L, 1993L, 1993L, 1993L, 
1993L, 1993L)), class = "data.frame", row.names = c(NA, -16L
))

我想要的:

数据中有四列:key、rr、dist和year。

我想根据每年唯一的“关键”值得到RR的总和,这样“dist”就小于或等于1100。

到目前为止我有:

我正在处理多个文件,因此脚本如下:

dat<-read.csv("test_dat.csv",header=T,stringsAsFactors=FALSE)

dat2<-dat[which(dat$dist <= 1100),]
dat3<-as.data.frame(cbind(dat2$RR,dat2$Year))
colnames(dat3)<-c("RR","Year")
agg<-aggregate(.~Year,dat3,sum,na.rm=T)

write.csv(agg,file="test.csv",row.names=T)

我能在R里怎么做吗? 我会感谢你的帮助。