[R] Help in getting aggregated data

[Gabor Grothendieck]

Try this:

aggregate(a[3], a[1:2], max)


On 3/31/07, Deepak Manohar <deepakmanohar at gmail.com> wrote:
> Hi team,
>   I have the data of the form:
>
> > a<- data.frame(x=c(1,2,1,4,3), y=c(1,2,1,4,3), z=c(1,2,3,4,5))
>
> I need the output of the form
>
> > b<- data.frame(x=c(1,2,3,4), y=c(1,2,3,4), z=(3,2,5,4) )
>
> As you can see, the Z value contains the maximum for each of the (x,y)
> combinations.
>
> I used
> > c<-by(a$z, list(x=a$x, y=a$y), max)
> > c[,]
>   y
> x    1  2  3  4
>  1  3 NA NA NA
>  2 NA  2 NA NA
>  3 NA NA  5 NA
>  4 NA NA NA  4
>
> Not sure If I have any standard function to convert this to the data
> frame that I need. Can you help me convert the last array into the
> data frame? If there is any other way apart from using the "by"
> function, please inform me regarding that as well.
>
> -- Deepak Manohar T
>
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