[R] Help summarizing R data frame

[jim holtman]

Nice thing about R is there are a number of ways to do things:

> x
  identifier quantity
1          1       10
2          1       20
3          2       30
4          1       15
5          2       10
6          3       20
> require(sqldf)
> sqldf('select identifier, sum(quantity) as quantity from x group by identifier')
  identifier quantity
1          1       45
2          2       40
3          3       20
>

or using 'data.table'

> require(data.table)
Loading required package: data.table
> x <- data.table(x)
> x[, sum(quantity), by = identifier]
     identifier V1
[1,]          1 45
[2,]          2 40
[3,]          3 20


On Thu, Dec 2, 2010 at 11:24 AM, chris99 <cheakes at hotmail.com> wrote:
>
> 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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> Sent from the R help mailing list archive at Nabble.com.
>
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?