r - Filter data.table on multiple criteria in the same column -

r - Filter data.table on multiple criteria in the same column -

i have next data.table:

> dt= data.table(num=c(1,2,1,1,2, 3, 3,2), letters[1:8]) > dt num v2 1: 1 2: 1 c 3: 1 d 4: 2 b 5: 2 e 6: 2 h 7: 3 f 8: 3 g

i want filter num equals 1 , 2 , resulting data.table. can with:

> dt[num==1 | num==2,] num v2 1: 1 2: 1 c 3: 1 d 4: 2 b 5: 2 e 6: 2 h

or:

rbind(setkey(dt, num)[j(1)],setkey(dt, num)[j(2)])

but there alternative setkey sec look shorter like:

setkey(dt, num)[1|2]

since setkey code quicker big amount ... appreciate help!

in additions kfb's comment:

setkey(dt, num)[num %in% c(1,2)]

if filtering values integers in sequence:

setkey(dt,num)[j(1:2)] # or setkey(dt,num)[seq]

if arbitrary:

setkey(dt,num)[j(c(1,2)]

note 1: may not work in older versions of data.table note 2: . alias j more readable:

setkey(dt,num)[.(1:2)]

fwiw, using magrittr bundle data.table , making clear possible:

dt %>% setkey(num) dt[ .(1:2) ]

the drawback can't neatly on 1 line.

r data.table