I have customer data grouped by customer ID and ordered by date of purchase. I want to add a column that cumulatively counts the number of distinct products that have been ordered to date - i.e:
Input <- data.frame(Customer = c("C-01", "C-01", "C-02", "C-02", "C-02", "C-02", "C-03", "C-03", "C-03", "C-03"),
Product = c("COKE", "COKE", "FRIES", "SHAKE", "BURGER", "BURGER", "CHICKEN", "FISH", "FISH", "FISH"),
Date = c("2018-01-02","2018-01-05","2018-01-03","2018-01-06","2018-01-08","2018-01-12","2018-01-02","2018-01-04", "2018-01-16", "2018-01-20"))
Output <- data.frame(Customer = c("C-01", "C-01", "C-02", "C-02", "C-02", "C-02", "C-03", "C-03", "C-03", "C-03"),
Product = c("COKE", "COKE", "FRIES", "SHAKE", "BURGER", "BURGER", "CHICKEN", "FISH", "FISH", "FISH"),
Date = c("2018-01-02","2018-01-05","2018-01-03","2018-01-06","2018-01-08","2018-01-12","2018-01-02","2018-01-04", "2018-01-16", "2018-01-20"),
Cum_Distinct = c(1, 1, 1, 2, 3, 3, 1, 2, 2, 2))
With the Input data set, I want to create the output data using dplyr. How do I keep a cumulative count of distinct products encountered to date?