I have data in which subjects completed multiple ratings per day over 6-7 days. The number of ratings per day varies. The data set includes subject ID, date, and the ratings. I would like to create a new variable that recodes the dates for each subject into "study day" --- so 1 for first day of ratings, 2 for second day of ratings, etc.
For example, I would like to take this:
id Date Rating
1 10/20/2018 2
1 10/20/2018 3
1 10/20/2018 5
1 10/21/2018 1
1 10/21/2018 7
1 10/21/2018 9
1 10/22/2018 4
1 10/22/2018 5
1 10/22/2018 9
2 11/15/2018 1
2 11/15/2018 3
2 11/15/2018 4
2 11/16/2018 3
2 11/16/2018 1
2 11/17/2018 0
2 11/17/2018 2
2 11/17/2018 9
And end up with this:
id Day Date Rating
1 1 10/20/2018 2
1 1 10/20/2018 3
1 1 10/20/2018 5
1 2 10/21/2018 1
1 2 10/21/2018 7
1 2 10/21/2018 9
1 3 10/22/2018 4
1 3 10/22/2018 5
1 3 10/22/2018 9
2 1 11/15/2018 1
2 1 11/15/2018 3
2 1 11/15/2018 4
2 2 11/16/2018 3
2 2 11/16/2018 1
2 3 11/17/2018 0
2 3 11/17/2018 2
2 3 11/17/2018 9
I was going to look into setting up some kind of loop, but I thought it would be worth asking if there is a more efficient way to pull this off. Are there any functions that would allow me to automate this sort of thing? Thanks very much for any suggestions.
Since you want to reset the count after every id , makes this question a bit different.
Using only base R, we can split the Date based on id and then create a count of each distinct group.
df$Day <- unlist(sapply(split(df$Date, df$id), function(x) match(x,unique(x))))
df
# id Date Rating Day
#1 1 10/20/2018 2 1
#2 1 10/20/2018 3 1
#3 1 10/20/2018 5 1
#4 1 10/21/2018 1 2
#5 1 10/21/2018 7 2
#6 1 10/21/2018 9 2
#7 1 10/22/2018 4 3
#8 1 10/22/2018 5 3
#9 1 10/22/2018 9 3
#10 2 11/15/2018 1 1
#11 2 11/15/2018 3 1
#12 2 11/15/2018 4 1
#13 2 11/16/2018 3 2
#14 2 11/16/2018 1 2
#15 2 11/17/2018 0 3
#16 2 11/17/2018 2 3
#17 2 11/17/2018 9 3
I don't know how I missed this but thanks to @thelatemail who reminded that this is basically the same as
library(dplyr)
df %>%
group_by(id) %>%
mutate(Day = match(Date, unique(Date)))
AND
df$Day <- as.numeric(with(df, ave(Date, id, FUN = function(x) match(x, unique(x)))))