R lag/lead - how to ignore rows before and after existing rows

Question

I have this dataframe in R

   id      a        b        c        d
1  42      3        2       NA        5
2  42     NA        6       NA        6
3  42      1       NA        7        8

With function like this

library(dplyr)

dataframe %>%
 mutate(e = lead(d))

I get at third row NA since there is not fourth row, but how can I get value from first row - 5? Result should look like this

   id      a        b        c        d         e
1  42      3        2       NA        5         6
2  42     NA        6       NA        6         8
3  42      1       NA        7        8         5

I edited the question to make it more clear. – Jack_Carver Jul 07 '18 at 19:54 — Jack_Carver, Jul 07 '18 at 19:54

score 3 · Accepted Answer · answered Jul 07 '18 at 19:58

3

We can use the first function in the default argument of the lead function.

library(dplyr)

dat2 <- dat %>%
  mutate(e = lead(d, default = first(d)))
dat2
#   id  a  b  c d e
# 1 42  3  2 NA 5 6
# 2 42 NA  6 NA 6 8
# 3 42  1 NA  7 8 5

DATA

dat <- read.table(text = "   id      a        b        c        d
1  42      3        2       NA        5
2  42     NA        6       NA        6
3  42      1       NA        7        8",
                  header = TRUE)

answered Jul 07 '18 at 19:58

www

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Is there a benefit of using `first(d)` over `d[1]` or is it personal preference? – Dan Nov 23 '18 at 16:56
1

@Lyngbakr I think it is personal preference. – www Nov 23 '18 at 19:13

R lag/lead - how to ignore rows before and after existing rows

1 Answers1