By "group" I mean rows with the same value in one of their columns, not the dplyr grouping. This is a sample dataframe I'm working with.
df <- data.frame("participant" = c("jack", "ellen", "ellen", "jack", "denise"),
"food" = c(a, a, b, c, a),
"quantity" = c(3, 6, 2, 34, 2))
# participant food quantity
#1 jack a 3
#2 ellen a 6
#3 ellen b 2
#4 jack c 34
#5 denise a 2
I would like to add a percentage column to this dataframe that is $quantity / sum $quantity for unique participant. Something like this:
participant food quantity percent
1 jack a 3 8
2 ellen a 6 75
3 ellen b 2 25
4 jack c 34 92
5 denise a 2 100
I would like it to be done automatically without me manually writing the values in per row. How would I write the code to do that?
