aggregate and sum on some columns fromduplicate rows

Hi,
You could use ?ddply
library(plyr)

cbind(ddply(dat,.(St.Sam,Sp),function(x) x[!duplicated(x$Var1),])[,-c(5:6)],ddply(dat,.(St.Sam,Sp),colwise(sum,.(NT,PT)))[,-c(1:2)])
?? St.Sam? Sp Var1 Var2 NT PT
1? ST1.S1 Sp1?? 12?? aa 23 37
2? ST1.S1 Sp2?? 32?? bb 45 26
3? ST1.S1 Sp3?? 47?? cc 89 35
4? ST1.S2 Sp1?? 25?? dd 29 66
5? ST1.S2 Sp2?? 59?? ee 89 35
6? ST2.S1 Sp1?? 15?? aa 30 45
7? ST2.S1 Sp2?? 45?? cc 55 23
8? ST2.S1 Sp3?? 27?? aa 85 12
9? ST2.S1 Sp4?? 42?? cc? 8? 3
10 ST3.S1 Sp1?? 25?? aa 26 69
11 ST3.S1 Sp2?? 36?? bb 65 48
A.K.

Hi again,

Sorry for disturbing. After posting I suddenly found a solution.
As it may help someone else here it goes.

df
du1 <- duplicated(df[,c("St.Sam","Species")],fromLast = F)
du2 <- duplicated(df[,c("St.Sam","Species")],fromLast = T)
X <- df[du1|du2,]
aggRows <- aggregate(cbind(NT,PT) ~St.Sam+Species+Var1+Var2, X,sum)
dfNew <- rbind(df[!(du1|du2),], aggRows)

Just need to "polish" dfNew and its OK. But maybe there is a more elegant
solution.

Cheers,

Tito





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