# [R] selections of data by one variable

Uwe Ligges ligges at statistik.uni-dortmund.de
Wed May 4 15:27:58 CEST 2005

```Tu Yu-Kang wrote:

> Dear R experts,
>
> My problem is as follows:
>
> Suppose I have a data frame d comprising two variable a<-c(1:10) &
> b<-c(11:20).
>
> I now want to select a subgroup according the values of b.
>
> I know if I just want to select, say, b=17, I can use f<-d[d\$b==17] and
> R will give me
>
>> f
>
>  a  b
> 7 7 17
>
> However, if now I want to select a subgroup according to
> b==e<-c(13,15,17), then the same syntx doesn't work.

Which language is this???

To summarize, all the code you specified is:

a<-c(1:10) & b<-c(11:20)
f<-d[d\$b==17]
b==e<-c(13,15,17)

In R, each line for itself is syntacically completely incorrect (even if
you say something would work, which is definitely not the case)!

I guess you want something like

d <- data.frame(a = 1:10, b = 11:20)
subset(d, b == 17)
e <- c(13, 15, 17)
subset(d, b %in% e)

Uwe Ligges

> What is the correct way to do it?  My data have more than one million
> subjects, and I want to select part of them according to their id numbers.
>
> Your help will be highly appreciated.
>
> Best regards,
>
> Yu-Kang
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help