[R] Script for conditional sums of vectors

[Rui Barradas]

Hello,

In what follows, I've renamed the data.frame 'dat', 'data' already is an 
R function.

xtabs(c ~ a + b, data = dat)


Hope this helps,

Rui Barradas

Em 04-02-2013 09:29, Benjamin Gillespie escreveu:
> 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 at 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.
>