r - "if" function for year and day -

in dataset have data 2 years, there 730 entries. problem is, column "day of year" has form 1 365 year 1 , same year 2.

i want values in column "day of year" 1 730.

my "newbie-function":

set$doynew = if (seq(set$year==2002)) {set$doy <- set$doy+365}

doesn´t me further. error gets is:

in if (z < 0) { :> condition has length > 1 , first element used

where problem?

the error telling clause if should single value.
ie, either true or false, not eg c(true, true, false) .

so if trying accomplish

if (c(true, false, true))   < when true >   < different when false >

a basic if statement not work.
statement @ first value (as warning indicates).

for such situations, statement use ifelse (as @joran pointed out in answer)

ifelse ( c(true, false, true),    < when true > ,    < different when false > )

set$doynew <- ifelse(set$year == 2002,doy + 365,doy)

additionally, if data in data.frame, can subset needed:

 mydf$day[mydf$year==2002] <- 365 + mydf$day[mydf$year==2002]   # or if using data.table:    mydt[year==2002, day := day + 365]

Bready