Hello

I have a dataset with lots of repeated measures and dates. I currently have this in the long format

Patient ID . Chemotherapy date blood test date
a 1/5/19 29/4/19
a . 1/5/19

I am trying to group the blood test dates for the patients with the corresponding chemotherapy date. I have all the dates in STATA format. Then I want to understand how many tests typically a patient will have for each of their chemotherapy dates. I am really stuck as how to do this as I am fairly new to STATA.

Would be grateful for any advice or pointers!