Create recursive variables in tidy

I'm trying to make a tidy solution to create an duration variable based on whether some event has happened or not. This is very simple to do in a for loop as

    library(tidyverse)
    df <- tibble(event = c(0,0,0,0,1,0,0,1,1,0,0,1))
    df$dur <- NA
    df$dur[1]<-0 
    for(i in 2:nrow(df)){
    if(df$event[i]==0){
    df$dur[i] <- df$dur[i-1]+1
    }else{
    df$dur[i] <- 0
    }
    }
    print(df)

However, I cannot seem to find a tidy solution to this. I have tried using the purrr accumulate function but this gives me the wrong output

library(tidyverse)
df <- tibble(event = c(0,0,0,0,1,0,0,1,1,0,0,1))
df <- df %>% mutate(dur = case_when(event==1 ~ 0,
                        T~purrr::accumulate(event,~.x+1,.init=-1)[-1]))
print(df)

Any suggestion on how to do this?

Solution

Here is one way to do it capturing your groups via cumsum when event == 1, i.e.

library(dplyr)

df %>% 
 group_by(grp = cumsum(event == 1)) %>% 
 mutate(dur = seq(n()) - 1)

which gives,

# A tibble: 12 x 3
# Groups:   grp [5]
   event   grp   dur
   <dbl> <int> <dbl>
 1     0     0     0
 2     0     0     1
 3     0     0     2
 4     0     0     3
 5     1     1     0
 6     0     1     1
 7     0     1     2
 8     1     2     0
 9     1     3     0
10     0     3     1
11     0     3     2
12     1     4     0

NOTE: You can ungroup and remove the column grp at the end If you 'd like