I am trying to use the lead function on R, where basically the last value in val.test corresponding to the group var becomes the first value in val.test.lead
set.seed(14)
df <- data.frame(
var = c("A","B","C","D","E","F","G","H","I","J","K","L"),
val.test = rnorm(12,4,5)
)
df$var <- as.factor(df$var)
df <- df %>%
dplyr::group_by(var) %>%
dplyr::mutate(val.test.lead = lead(val.test, default = first(val.test)))
#The output is
var val.test val.test.lead
<fct> <dbl> <dbl>
1 A 0.691 0.691
2 B 12.6 12.6
3 C 14.6 14.6
4 D 11.5 11.5
5 E 3.82 3.82
6 F 10.2 10.2
7 G 3.68 3.68
8 H 9.34 9.34
9 I 2.12 2.12
10 J 9.22 9.22
11 K 2.09 2.09
12 L 5.50 5.50
#The expected output is
var val.test val.test.lead
<fct> <dbl> <dbl>
1 A 0.691 5.50
2 B 12.6 0.691
3 C 14.6 12.6
4 D 11.5 14.6
5 E 3.82 11.5
6 F 10.2 3.82
7 G 3.68 10.2
8 H 9.34 3.68
9 I 2.12 9.34
10 J 9.22 2.12
11 K 2.09 9.22
12 L 5.50 2.09
What you looking for is not lead, but lag.
comparing lead to lag,
set.seed(14)
df <- data.frame(
var = c("A","B","C","D","E","F","G","H","I","J","K","L"),
val.test = rnorm(12,4,5)
) %>% tibble()
df$var <- as.factor(df$var)
df %>% mutate(val.test.lag = lag(val.test, default=last(val.test)),
val.test.lead = lead(val.test,default = first(val.test)))
Output
# A tibble: 12 × 4
var val.test val.test.lag val.test.lead
<fct> <dbl> <dbl> <dbl>
1 A 0.691 5.50 12.6
2 B 12.6 0.691 14.6
3 C 14.6 12.6 11.5
4 D 11.5 14.6 3.82
5 E 3.82 11.5 10.2
6 F 10.2 3.82 3.68
7 G 3.68 10.2 9.34
8 H 9.34 3.68 2.12
9 I 2.12 9.34 9.22
10 J 9.22 2.12 2.09
11 K 2.09 9.22 5.50
12 L 5.50 2.09 0.691
Created on 2022-04-30 by the reprex package (v2.0.1)