Create a variable based on the order on a specific value of another variable

Question

I have a dataframe similar to this (although more complex):

id <- rep(1:2, each = 4)
Cond <- rep(c("test", "test","form", "form", "form", "form", "test","test"))

df <- data.frame(id,Cond)

I would like to create a third variable in my dataframe that tells me the order of Cond for each ID. For example, the first participants had first the test and then the form. In the end, the dataframe would look like this:

 id Cond order
  1 test test-form
  1 test test-form
  1 form test-form
  1 form test-form
  2 form form-test
  2 form form-test
  2 test form-test
  2 test form-test

Any help would be much appreciated

akrun · Accepted Answer · 2020-04-29 20:40:00Z

1

We can check the first element of each 'id' to paste the 'form' or 'test'

library(dplyr)
library(stringr)
df %>% 
    group_by(id) %>%
    mutate(order = str_c(first(Cond), setdiff(c('form', 'test'), 
               first(Cond)), sep='-'))
# A tibble: 8 x 3
# Groups:   id [2]
#     id Cond  order    
#  <int> <fct> <chr>    
#1     1 test  test-form
#2     1 test  test-form
#3     1 form  test-form
#4     1 form  test-form
#5     2 form  form-test
#6     2 form  form-test
#7     2 test  form-test
#8     2 test  form-test

edited Apr 29, 2020 at 20:40

answered Apr 29, 2020 at 20:08

akrun

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1 Comment

unomas83 Over a year ago

Thanks a lot for your reply. Unfortunately, that code doesn't give you the output that I want. For example, for the id 1, your ouput gives this sequence test-form, test-form, form-test, form-test. And for this particpants all should be test-form

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