> merge(t2, paar, by.x="number", by.y="nr")
  number taht paaritu sona
1      1    a       1  yks
2      2    b       2 kaks
> t2
  taht number paaritu
1    a      1       1
2    b      2       2
3    c      3       1
4    d      4       2
5    e      5       1
6    f      6       2
> paar
  nr sona
1  1  yks
2  2 kaks


> aggregate(mtcars[c("cyl", "wt")], by=list(mtcars$am), FUN=mean)
  Group.1      cyl       wt
1       0 6.947368 3.768895
2       1 5.076923 2.411000



> paste("v", 1:3)
[1] "v 1" "v 2" "v 3"
> paste("v", 1:3, sep="")
[1] "v1" "v2" "v3"


> mtcars[mtcars$am==1, c("cyl", "mpg")]
               cyl  mpg
Mazda RX4        6 21.0
Mazda RX4 Wag    6 21.0
Datsun 710       4 22.8
Fiat 128         4 32.4
Honda Civic      4 30.4
Toyota Corolla   4 33.9
Fiat X1-9        4 27.3
Porsche 914-2    4 26.0
Lotus Europa     4 30.4
Ford Pantera L   8 15.8
Ferrari Dino     6 19.7
Maserati Bora    8 15.0
Volvo 142E       4 21.4
> subset(mtcars, am==1, select=c(cyl, mpg))
               cyl  mpg
Mazda RX4        6 21.0
Mazda RX4 Wag    6 21.0
Datsun 710       4 22.8
Fiat 128         4 32.4
Honda Civic      4 30.4
Toyota Corolla   4 33.9
Fiat X1-9        4 27.3
Porsche 914-2    4 26.0
Lotus Europa     4 30.4
Ford Pantera L   8 15.8
Ferrari Dino     6 19.7
Maserati Bora    8 15.0
Volvo 142E       4 21.4