> x<-c(0,-3,4,-1,45,90,5)
> x>0
[1] FALSE FALSE  TRUE FALSE  TRUE  TRUE  TRUE

> x[x>0]
[1]  4 45 90  5

> x[x>5 | x<(-2)]
[1] -3 45 90
> x[x>1 & x<20]
[1] 4 5

> x[-1]
[1] -3  4 -1 45 90  5
> x[-c(3,4)]
[1]  0 -3 45 90  5

> ph<-c(4.5,7,7.3,8.2,6.3)
> names(ph)<-c("area1","area2","mud","dam","middle")
> ph["mud"]
mud
7.3