[R] Help summarizing R data frame

[Patrick Hausmann]

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!