flag = 1 if there is a change from 1 to 0 in R-CodePudding

Is there a quick way to assign flag to 1 if for a particular variable there is a change from 1 to 0, so that I get the below. This variable is only allowed to go from from 0 to 1, it is not possible to see 1 to 0 and I would like to flag if that happens.

organisation | time       | variable | flag
A            | 2020-01-01 | 0        | 0
A            | 2020-02-01 | 0        | 0   
A            | 2020-03-01 | 0        | 0   
A            | 2020-04-01 | 1        | 0       
A            | 2020-05-01 | 1        | 0      
A            | 2020-06-01 | 1        | 0     
A            | 2020-07-01 | 1        | 0    
B            | 2020-01-01 | 0        | 1      
B            | 2020-02-01 | 0        | 1     
B            | 2020-03-01 | 0        | 1     
B            | 2020-04-01 | 1        | 1       
B            | 2020-05-01 | 0        | 1      
B            | 2020-06-01 | 1        | 1     
B            | 2020-07-01 | 1        | 1

Many thanks

CodePudding user response：

Thank you for clarifying your problem in your comment and edited question. Here is a potential solution that I think will work with your actual data:

library(tidyverse)

df <- data.frame(
  stringsAsFactors = FALSE,
            organisation = c("A","A","A","A",
                             "A","A","A","B","B","B","B","B","B","B"),
                    time = c("2020-01-01",
                             "2020-02-01","2020-03-01","2020-04-01","2020-05-01",
                             "2020-06-01","2020-07-01","2020-01-01",
                             "2020-02-01","2020-03-01","2020-04-01","2020-05-01",
                             "2020-06-01","2020-07-01"),
                variable = c(0L,0L,0L,1L,1L,
                             1L,1L,0L,0L,0L,1L,0L,1L,1L),
                    flag = c(0L,0L,0L,0L,0L,
                             0L,0L,1L,1L,1L,1L,1L,1L,1L)
      )

df %>%
  group_by(organisation) %>%
  mutate(flag =  any(lag(variable, default = 0) == 1 & variable == 0))
#> # A tibble: 14 × 4
#> # Groups:   organisation [2]
#>    organisation time       variable  flag
#>    <chr>        <chr>         <int> <int>
#>  1 A            2020-01-01        0     0
#>  2 A            2020-02-01        0     0
#>  3 A            2020-03-01        0     0
#>  4 A            2020-04-01        1     0
#>  5 A            2020-05-01        1     0
#>  6 A            2020-06-01        1     0
#>  7 A            2020-07-01        1     0
#>  8 B            2020-01-01        0     1
#>  9 B            2020-02-01        0     1
#> 10 B            2020-03-01        0     1
#> 11 B            2020-04-01        1     1
#> 12 B            2020-05-01        0     1
#> 13 B            2020-06-01        1     1
#> 14 B            2020-07-01        1     1

^{Created on 2022-07-18 by the reprex package (v2.0.1)}