conditionally replace values in next row

Question

How can I write a conditional function that compares entries in rows of a data frame in R. For example if entry in row 1 is greater than entry in row 2 replace row 2 entry with "lower"

row1 row2
667  668    
673  674
665  679 
664  668 

Entries in first column will be higher,lower,lower if the function is applied.

Answer 1

You can use an ifelse:

dat$row2 <- ifelse(dat$row1 < dat$row2, "higher", "lower")

Answer 2

We could do

dat1 <- dat
dat1[] <- c('lower', 'higher')[t(apply(dat, 1, order))]