Shift values in single column of dataframe up
Your problem simplifies to:
- Drop the first
n
elements in a vector - Pad
n
values ofNA
at the end
You can do this with a simple function:
shift <- function(x, n){
c(x[-(seq(n))], rep(NA, n))
}
example$z <- shift(example$z, 2)
The result:
example
x y z
1 1 1 3
2 2 2 4
3 3 3 5
4 4 4 6
5 5 5 7
6 6 6 8
7 7 7 NA
8 8 8 NA
I couldn't find a good duplicate, so here's another solution using length<-
shift2 <- function(x, n) `length<-`(tail(x, -n), length(x))
# or just shift2 <- function(x, n) c(tail(x, -n), rep(NA, n))
transform(example, z = shift2(z, 2))
# x y z
# 1 1 1 3
# 2 2 2 4
# 3 3 3 5
# 4 4 4 6
# 5 5 5 7
# 6 6 6 8
# 7 7 7 NA
# 8 8 8 NA
example = tibble(x=c(1,2,3,4,5,6,7,8),
y=c(1,2,3,4,5,6,7,8),
z=c(1,2,3,4,5,6,7,8))
example %>% mutate_at(c("z"), funs(lead), n = 2 )
# A tibble: 8 x 3
x y z
<dbl> <dbl> <dbl>
1 1.00 1.00 3.00
2 2.00 2.00 4.00
3 3.00 3.00 5.00
4 4.00 4.00 6.00
5 5.00 5.00 7.00
6 6.00 6.00 8.00
7 7.00 7.00 NA
8 8.00 8.00 NA