Logical Operators

== Equal != Different

> Greater than < Lower than

>= Greater or equal <= Lower or equal

& and | or ! not

T true F false

dat[dat$v1 == 'yes',]

dat[dat$v1 == 'yes' & dat$v2 !='Q1',]

if(!error) dat$dv=log(dat$dv) else dat$dv=NA

dat[scale(dat$dv) >= 2 | scale(dat$dv <= -2),'dv']=NA

dat[abs(scale(dat$dv)) >= 2, 'dv']=NA