Changing the row id conditional on a different column?

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Hi I have a data set like this

df <- cbind(c("id",1,2,3,4,5,6,7,8,9,10,11), c("trial",1,1,1,1,1,1,2,2,2,2,2))

However, I want to change the ids conditional on the trial number - something like this

df1 <- cbind(c("id",1.1,1.2,1.3,1.4,1.5,1.6,2.1,2.2,2.3,2.4,2.5), c("trial",1,1,1,1,1,1,2,2,2,2,2))

I would really appreciate it if someone could help me with this. I am still learning R.

r
1 Answers
df <- data.frame(id = c(1,2,3,4,5,6,7,8,9,10,11), trial = c(1,1,1,1,1,1,2,2,2,2,2))

library(dplyr)

df |> 
  arrange(trial, id) |> 
  group_by(trial) |> 
  mutate(trial_id = row_number()) |> 
  ungroup() |> 
  mutate(id = as.numeric(paste0(trial, ".", trial_id)))
  # OR use: tidyr::unite("id", c(trial, trial_id), sep = ".", remove = FALSE)

# A tibble: 11 × 3
      id trial trial_id
   <dbl> <dbl>    <int>
 1   1.1     1        1
 2   1.2     1        2
 3   1.3     1        3
 4   1.4     1        4
 5   1.5     1        5
 6   1.6     1        6
 7   2.1     2        1
 8   2.2     2        2
 9   2.3     2        3
10   2.4     2        4
11   2.5     2        5
Phil0
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