Let's say I have this df (but with thousand of IDs and tens of treatments)
df = data.frame(ID = c(1,1,1,2,2,2,2,2),
treatment = c('AB','CD','EF','AB','CD','GH','IM','LN') )
I wish to obtain the following output
ID treatment_1 treatment_2 treatment_3 treatment_4 treatment_5
1 1 AB CD EF <NA> <NA>
2 2 AB CD GH IM LN
What I don't want
ID .by Treatment_1 Treatment_2 Treatment_3 Treatment_4 Treatment_5 Treatment_6 Treatment_7 Treatment_8
<dbl> <dbl> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <chr>
1 1 1 AB CD EF NA NA NA NA NA
2 2 2 NA NA NA AB CD GH IM LN