I would like to subset my data frame to keep only groups that have 3 or more observations on DIFFERENT days. I want to get rid of groups that have less than 3 observations, or the observations they have are not from 3 different days.
Here is a sample data set:
Group Day
1 1
1 3
1 5
1 5
2 2
2 2
2 4
2 4
3 1
3 2
3 3
4 1
4 5
So for the above example, group 1 and group 3 will be kept and group 2 and 4 will be removed from the data frame.
I hope this makes sense, I imagine the solution will be quite simple but I can't work it out (I'm quite new to R and not very fast at coming up with solutions to things like this). I thought maybe the diff function could come in handy but didn't get much further, and I didn't have any luck searching existing questions on SO and other websites for an answer.
Thank you very much in advance!