Hello,

I am trying to figure out a code that would allow me create a column that counts the number of unique observations each subject in my data set has. These observations would be distinguishable by a study ID and a date. I then want the column to contain a number that is the same number repeated for a given study subject that gives the total observations. For example, columns 1 and 2 below are an example of what I have and Col3 is what I would want to generate:
Col1 Col2 Col3
Subject1 23jan2019 2
Subject1 15sept2018 2
Subject1 3may2017 3
Subject2 2mar2019 3
Subject2 15sept2018 3
Subject3 2jun2019 4
Subject3 2jun2019 4
Subject3 5july2018 4
Subject3 7jan2018 4
Subject3 6oct2017 4
Subject4 7feb2019 1

Column 3 is what I would want that says how many unique data points that subject has. Because subject 3 has two data points on the same day they only have 4 unique points reflected in col3.

Thank you in advance!