Here are some examples with tapply, aggregate, ddply:
x <- read.table("clipboard", head=TRUE)
with(x, tapply(quantity, identifier, sum))
aggregate(x$quantity, by=list(x$identifier), sum)
aggregate(quantity ~ identifier, data = x, sum)
library(plyr)
ddply(x, .(identifier), summarise, quantity=sum(quantity))
HTH
Patrick
Am 02.12.2010 17:24, schrieb chris99:
I am trying to aggregate data in column 2 to identifiers in col 1
eg..
take this>
identifier quantity
1 10
1 20
2 30
1 15
2 10
3 20
and make this>
identifier quantity
1 45
2 40
3 20
Thanks in advance for your help!
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