[R] Assigning value of subset argument in "subset" function

[David Winsemius]

On Aug 23, 2009, at 9:56 PM, Steven Kang wrote:

> Dear R users,
>
> I am using "subset" function to filter out specific conditions and  
> would
> like to use the value of subsetted argument as a name of an object.
>
> Specifically, from the following statement:
>
>     a <- subset(dat, dat$x == "A" & dat$xx == 1 & dat$xxx == "AB" &  
> dat$y
> == "B" & dat$yy == 2)
> I would to assign the value of the 3rd subset argument (i.e. "AB")  
> as an
> object's name such as:
>
>     a.AB <- sum(a$z)

Sounds like you need to read FAQ 7.21:

http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-can-I-turn-a-string-into-a-variable_003f

Perhaps, ... lightly tested, of course, because no reproducible data  
provided:

assign( paste("a.",  sum(a$z), sep=""),
         subset(dat,x == "A" & xx == 1 & xxx == "AB" &  y== "B" & yy  
== 2)   )

  # you do not need the "dat$"'s in the subset.

 > a <- data.frame(x=1:4, y=4:7, xx=8:11, xxx=12:15)
 > a
   x y xx xxx
1 1 4  8  12
2 2 5  9  13
3 3 6 10  14
4 4 7 11  15

 > a.10
   x y xx xxx
1 1 4  8  12
-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT