Creating a column based on values of another column in a data frame-CodePudding

Considering the following dataset:

df <- data.frame (Treatment = c("Low", "Low", "Low", "Med", "Med", "High", "High", "Med", "Low", "Med", "High", "High"), 
Value = c( 23,4,56,76,89,86,66,31,48,51,75,101))

Treatment	Value
Low	23
Low	4
Low	56
Med	76
Med	89
High	86
High	66
Med	31
Low	48
Med	51
High	75
High	101

and I would like to create a column so the data frame looks like:

Treatment	Value	I.D
Low	23	Low1
Low	4	Low2
Low	56	Low3
Med	76	Med1
Med	89	Med2
High	86	High1
High	66	High2
Med	31	Med3
Low	48	Low4
Med	51	Med4
High	75	High3
High	101	High4

Basically I'd like to create a column with individual ID for each row based on the level they belong to.

I have tried this:

df %>% group_by (Treatment) %>%
          mutate (I.D = case_when(
                     Treatment == "Low" ~ paste ("Low",seq(1,4)),     
                     Treatment == "Med" ~ paste ("Med",seq(1,4)),
                     Treatment == "High" ~ paste("High",seq(1,4))))

Thanks very much in advance

CodePudding user response：

You can use row_number():

library(dplyr)
df |>
        group_by(Treatment) |> 
        mutate(id = paste0(Treatment, row_number()))

Output:

#> # A tibble: 12 x 3
#> # Groups:   Treatment [3]
#>    Treatment Value id   
#>    <chr>     <dbl> <chr>
#>  1 Low          23 Low1 
#>  2 Low           4 Low2 
#>  3 Low          56 Low3 
#>  4 Med          76 Med1 
#>  5 Med          89 Med2 
#>  6 High         86 High1
#>  7 High         66 High2
#>  8 Med          31 Med3 
#>  9 Low          48 Low4 
#> 10 Med          51 Med4 
#> 11 High         75 High3
#> 12 High        101 High4

^{Created on 2022-06-14 by the reprex package (v2.0.1)}

CodePudding user response：

If you don't want the whitespace after "Low" just use paste0 instead of 'paste'