使用变量/列 i R 的唯一值循环所有观察值

Question

I have dataset that looks like this:

Chain	Product	Week	Sales
Chain1	Prod1	1	0
Chain1	Prod1	2	0
--------	--------	-----	-----
Chain1	Prod1	51	10
Chain1	Prod1	52	14
Chain2	Prod1	1	10
Chain2	Prod1	2	11
--------	--------	-----	-----
Chain2	Prod1	51	12
Chain2	Prod1	52	15
Chain1	Prod2	1	3
Chain1	Prod2	2	4
--------	--------	-----	-----
Chain1	Prod2	51	8
Chain1	Prod2	52	10
Chain2	Prod2	1	11
Chain2	Prod2	2	12
--------	--------	-----	-----
Chain2	Prod2	51	15
Chain2	Prod2	52	7

This means I have weekly observations of sales for different products and chains. I would like to create an innovation dummy-variable which is equal to 1 when a new product is launched. This is the case for Product 1 in Chain 1 in week 51 (here, the sale goes from 0 to 10 in week 51, assuming that the sales are 0 between week 2 and 50). I then want my dummy, I, to be 1:

Chain	Product	Week	Sales	I
Chain1	Prod1	1	0	0
Chain1	Prod1	2	0	0
--------	--------	-----	-----	-
Chain1	Prod1	51	10	1
Chain1	Prod1	52	14	0
Chain2	Prod1	1	10	0
Chain2	Prod1	2	11	0
--------	--------	-----	-----	-
Chain2	Prod1	51	12	0
Chain2	Prod1	52	15	0
Chain1	Prod2	1	3	0
Chain1	Prod2	2	4	0
--------	--------	-----	-----	-
Chain1	Prod2	51	8	0
Chain1	Prod2	52	10	0
Chain2	Prod2	1	11	0
Chain2	Prod2	2	12	0
--------	--------	-----	-----	-
Chain2	Prod2	51	15	0
Chain2	Prod2	52	7	0

I would guess I should create a loop that loops over the weekly observations of sale for each type of product in each chain and detects the when the sale starts at 0 and then changes to some value. How should this be done in R?

Thank you.

Answer 1

For each Product in each Chain we can find the row where first time the Sale value was greater than 0 and change that row value to 1. If your data is called df .

library(dplyr)

df %>%
  group_by(Chain, Product) %>%
  mutate(I = as.integer(row_number() == match(TRUE, Sale > 0))) -> result

result

Answer 2

We can use base R

df$I <- with(df, ave(Sale > 0, Chain, Product, FUN = which.max))