How to create treatment variables to specify pre- and post-treatment periods for diff-in-diff in r?

Question

I am performing a diff-in-diff analysis with three interventions: the first in 2014, the second in 2015 and the third in 2018. My code is:

set.seed(30)
n <-9
dat <- data.frame(ID=1:n, 
                  year=c("2020", "2019", "2018", "2017", "2016", "2015", "2014", "2013", "2012"))
dat
  ID year
1  1    1
2  2    2
3  3    3
4  4    4
5  5    5
6  6    6
7  7    7
8  8    8
9  9    9

In order to perform the analysis, I need three columns in my data frame which indicate for each threatment period the pre- or post-treatment period with either a 0 or 1. I tried it myself and do always receive an error message saying "Error in mutate(): ! Problem while computing treatment = ifelse(year < 2014, "0", ifelse(year >= 2015, "1")). i The error occurred in row 7. Caused by error in ifelse(): ! Argument "no" fehlt (ohne Standardwert) Backtrace:

1. all %>% rowwise %>% ...
2. base::ifelse(year >= 2015, "1""

My code is:

all <- all %>% rowwise %>% mutate(
  treatment = ifelse(year < 2014, "0",
                     ifelse(year >= 2015, "1"
                     )))

all <- all %>% rowwise %>% mutate(
  treatment1 = ifelse(year >= 2013 && year < 2015, "0",
                      ifelse(year < 2018, "1"
                      )))

all <- all %>% rowwise %>% mutate(
  treatment2 = ifelse(year >= 2015 && year < 2018, "0",
                      ifelse(year >= 2018, "1"
                      )))

I am trying here not to have any overlaps in the periods to create unique periods in order to better extract the effects of each intervention. Unfortunately, I don't see the solution here. Any help would be amazing and much appreciated!

Best, Tobias