R - sapply function with multiple arguments [duplicate]

Question

This question already has answers here:

use multiple columns as variables with sapply (4 answers)

Closed 8 years ago.

I have a similar, but not quite the same question to R apply function with multiple parameters

I have a dataset with two variables RSHIFTSTART and RSHIFTEND (amongst other variables). These variables contain times eg. 23:30:00 or 00:00:00. I'd like to replace RSHIFTSTART and RSHIFTEND with NA wherever BOTH variables are zero ie. '00:00:00'.

I've written a function which I think may do the job:

# Change '00:00:00' to NA where both variables are '00:00:00'
zeroTime=function(x,y) {
    if (x=='00:00:00' & y=='00:00:00') {
        replace(x,x=='00:00:00',NA)
        replace(y,x=='00:00:00',NA)
    }
}

My question is how to apply this function to update the dataset's variable ie. supplying two arguments to it. I tried:

sapply(rosterSample$RSHIFTSTART,rosterSample$RSHIFTEND,zeroTime)

but this syntax is incorrect. Perhaps I'll be restricted to changing just one variable per call ie. RSHIFTSTART or RSHIFTEND, that's OK.

Any ideas? Thanks Pete

Answer 1

Something like this ?

rosterSample <- data.frame(RSHIFTSTART=c('00:00:00', '01:00:00', '00:00:00'), RSHIFTEND=c('10:00:00', '00:00:00', '00:00:00'), stringsAsFactors=FALSE)
ind <- with(rosterSample, RSHIFTSTART=='00:00:00' & RSHIFTEND=='00:00:00')
rosterSample$RSHIFTSTART[ind] <- NA
rosterSample$RSHIFTEND[ind] <- NA