CODEWITHSUNDEEP
r
user2242666
user2242666

Reputation: 211

Referring to previous row in R apply

Is there a way to refer to the previous row in apply's in R?

For example, my data.frame is sorted in the order of dates, and I want to find the differences between the date in the previous row and current row. This is easy in a loop. 

for( i in 2:nrow(Y)) {
      Y[i,]$window =  as.numeric(as.Date( Y[i, ]$start_date )  -  
                         as.Date( Y[i-1, ]$end_date ))
}

Can I do this using apply?

Upvotes: 3

Views: 1826

Answers (1)

mnel
mnel

Reputation: 115382

Try using head (or tail)

Y$window <- as.numeric(c(NA, as.Date(tail(y$start.date,-1)) - as.Date(head(y$end.date,-1)) ))

Upvotes: 1

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