Na fill after a specific value

Question

I would like to use NA.fill after a 1, but keep the NA’s after -1. Is there a simple solution for this?

Old	New
1	1
NA	1
NA	1
NA	1
-1	-1
NA	NA
NA	NA
1	1
NA	1
NA	1

Reproducible example data

dat <- read.table(text = "
Old New
1   1
NA  1
NA  1
NA  1
-1  -1
NA  NA
NA  NA
1   1
NA  1
NA  1", header = TRUE)

---

Edit: I only had 1s and -1s in the columns. Thank you all, the answers were very helpfull. My 'New' column is now exactly how I wanted.

Answer 1

You could do this by fill and ifelse

library(tidyverse)
dat <- structure(list(Old = c(1L, NA, NA, NA, -1L, NA, NA, 1L, NA, NA
)), row.names = c(NA, -10L), class = c("tbl_df", "tbl", "data.frame"
)) 

dat %>% 
mutate(New = Old) %>% 
fill(New) %>% 
mutate(New = ifelse(New == -1, Old, New)) %>% 
select(Old, New)

Result:

# A tibble: 10 x 2
     Old   New
   <int> <int>
 1     1     1
 2    NA     1
 3    NA     1
 4    NA     1
 5    -1    -1
 6    NA    NA
 7    NA    NA
 8     1     1
 9    NA     1
10    NA     1

I think SO this question could also be helpful.