Here are some examples of data aggregation functions in R:

http://www.slideshare.net/djandrija/data-aggregation-in-r

http://www.psychwire.co.uk/2011/04/data-aggregation-in-r-plyr-sqldf-and-data-table/

Andrija



On Mon, Feb 4, 2013 at 10:29 AM, Benjamin Gillespie <gybrg@leeds.ac.uk>wrote:

> Hi guys,
>
> I hope you can help me with this (probably) simple query:
>
> I have a data frame:
>
> --------------------------
>
> a=c(1,1,1,1,1,1,2,2,2,2,2,2)
> b=c(1,1,1,2,3,4,1,1,2,2,3,4)
> c=c(400,200,300,100,500,300,200,100,500,400,200,100)
>
>
> data=data.frame(a=a,b=b,c=c)
>
> --------------------------
>
> And I would like to get the following output:
>
> --------------------------
>
>         b
> a       1       2       3       4
> 1       900     100     500     300
> 2       300     900     200     100
>
> --------------------------
>
> The values in the output represent the sum of values "c" in data frame
> "data", for each "a" and "b" combination.
>
> For example, where "a" = 1 and "b" = 1, the output is 400+200+300 = 900.
>
> Please would anyone be able to provide a script to create my desired
> output?
>
> Many thanks in advance,
>
> Ben Gillespie
> Research Postgraduate
>
> School of Geography
> University of Leeds
> Leeds
> LS2 9JT
>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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