[R] logical operators in 'subset'

[Reitsma, Rene - COB]

Dear All, 

Am I correct in believing that logical operators such as && and ||
cannot be used as part of 
a 'subset' logical expression?

Example:

>foo = as.data.frame(matrix(c(1:9), nrow=3, ncol=3,
dimnames=list(c("r1","r2","r3"),c("c1","c2","c3"))))

>foo
   c1 c2 c3
r1  1  4  7
r2  2  5  8
r3  3  6  9

>subset(foo, c1 > 1)
   c1 c2 c3
r2  2  5  8
r3  3  6  9

>subset(foo, c2 > 5)
   c1 c2 c3
r3  3  6  9

However,

>subset(foo, c1 > 1 && c2 > 5)
[1] c1 c2 c3
<0 rows> (or 0-length row.names)

RR