On Fri, May 28, 2010 at 12:52 PM, Andre Easom <aea...@sportingindex.com> wrote:
> Hi,
>
> I'm a novice R user, much more used to SAS. My problem is pretty simple -
> basically, in a data frame, I have variables named
> x1,....,x10 and y1,...,y10; and I would like to create r1 = x1 / y1 etc
>
> Apologies if this is way too rudimentary - but I couldn't find any posts
> online which solve this exact issue.
Well, you can also access columns by number, so if you know what
columns your x's and y's are in you can do:
if you know the columns your x's and y's are in you can do it all at once:
3-column example:
> foo=data.frame(x1=1:10,x2=1:10,x3=1:10,y1=10:1,y2=runif(10),y3=runif(10))
> foo[,1:3]/foo[,4:6]
x1 x2 x3
1 0.1000000 2.037364 4.242166
2 0.2222222 38.651953 2.475068
3 0.3750000 9.351609 4.682223
etc
you can then add this to your data frame:
> foo=cbind(foo,foo[,1:3]/foo[,4:6])
> foo
x1 x2 x3 y1 y2 y3 x1 x2 x3
1 1 1 1 10 0.49083037 0.2357286 0.1000000 2.037364 4.242166
2 2 2 2 9 0.05174383 0.8080586 0.2222222 38.651953 2.475068
3 3 3 3 8 0.32080042 0.6407213 0.3750000 9.351609 4.682223
etc
and fix up the names:
> names(foo)[7:9]=paste("r",1:3,sep="")
> foo
x1 x2 x3 y1 y2 y3 r1 r2 r3
1 1 1 1 10 0.49083037 0.2357286 0.1000000 2.037364 4.242166
2 2 2 2 9 0.05174383 0.8080586 0.2222222 38.651953 2.475068
3 3 3 3 8 0.32080042 0.6407213 0.3750000 9.351609 4.682223
Barry
______________________________________________
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.
