Daniel,

You can see better what is going on if you look at

as.list(x)

There you can see that cyl and gear are vectors but mpg and hp are matrices.
You can rearrange them using the do.call() function

x2 <- do.call(cbind, x)
dim(x2)

Jean


On Fri, Nov 1, 2013 at 7:08 AM, Daniel Fernandes <daniel.fernandes@ine.pt>wrote:

>
>
> Hello,
>
>
>
> I´m using function aggregate in R 3.0.2.  If I run the instruction
> x<-aggregate(cbind(mpg,hp)~cyl+gear,data=mtcars,quantile) I get the
> result the following data.frame:
>
>
>
> cyl
>
> gear
>
> mpg.0%
>
> mpg.25%
>
> mpg.50%
>
> mpg.75%
>
> mpg.100%
>
> hp.0%
>
> hp.25%
>
> hp.50%
>
> hp.75%
>
> hp.100%
>
> 4
>
> 3
>
> 21.5
>
> 21.5
>
> 21.5
>
> 21.5
>
> 21.5
>
> 97
>
> 97
>
> 97
>
> 97
>
> 97
>
> 6
>
> 3
>
> 18.1
>
> 18.925
>
> 19.75
>
> 20.575
>
> 21.4
>
> 105
>
> 106.25
>
> 107.5
>
> 108.75
>
> 110
>
> 8
>
> 3
>
> 10.4
>
> 14.05
>
> 15.2
>
> 16.625
>
> 19.2
>
> 150
>
> 175
>
> 180
>
> 218.75
>
> 245
>
> 4
>
> 4
>
> 21.4
>
> 22.8
>
> 25.85
>
> 30.9
>
> 33.9
>
> 52
>
> 64.25
>
> 66
>
> 93.5
>
> 109
>
> 6
>
> 4
>
> 17.8
>
> 18.85
>
> 20.1
>
> 21
>
> 21
>
> 110
>
> 110
>
> 116.5
>
> 123
>
> 123
>
> 4
>
> 5
>
> 26
>
> 27.1
>
> 28.2
>
> 29.3
>
> 30.4
>
> 91
>
> 96.5
>
> 102
>
> 107.5
>
> 113
>
> 6
>
> 5
>
> 19.7
>
> 19.7
>
> 19.7
>
> 19.7
>
> 19.7
>
> 175
>
> 175
>
> 175
>
> 175
>
> 175
>
> 8
>
> 5
>
> 15
>
> 15.2
>
> 15.4
>
> 15.6
>
> 15.8
>
> 264
>
> 281.75
>
> 299.5
>
> 317.25
>
> 335
>
>
>
> So far so good, however the strange part happens when I run dim(x) or
> names(x), because the results are 8 4 (dim(x)) and "cyl"  "gear" "mpg"
> "hp" (names(x)). Why this occurs and how do I transform it in a regular
> data.frame with 12 columns?
>
>
>
> Thank you in advance,
>
>
>
> Daniel
>
>
>
> > sessionInfo()
>
> R version 3.0.2 (2013-09-25)
>
> Platform: i386-w64-mingw32/i386 (32-bit)
>
>
>
> locale:
>
> [1] LC_COLLATE=Portuguese_Portugal.1252
> LC_CTYPE=Portuguese_Portugal.1252
> LC_MONETARY=Portuguese_Portugal.1252 LC_NUMERIC=C
>
>
> [5] LC_TIME=Portuguese_Portugal.1252
>
>
>
> attached base packages:
>
> [1] grDevices datasets  splines   graphics  stats     tcltk     utils
> methods   base
>
>
>
> other attached packages:
>
> [1] svSocket_0.9-55 TinnR_1.0-5     R2HTML_2.2.1    Hmisc_3.12-2
> Formula_1.1-1   survival_2.37-4
>
>
>
> loaded via a namespace (and not attached):
>
> [1] cluster_1.14.4  grid_3.0.2      lattice_0.20-23 rpart_4.1-3
> svMisc_0.9-69   tools_3.0.2
>
>
>
>
>
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