Filter data based on lowest value

[williaml]

First of all, don't post screenshots of your data. Provide reproducible examples. It makes it easier for people to answer your question:

FAQ: What's a reproducible example (`reprex`) and how do I create one?

Why reprex? Getting unstuck is hard. Your first step here is usually to create a reprex, or reproducible example. The goal of a reprex is to package your code, and information about your problem so that others can run it and feel your pain. Then, hopefully, folks can more easily provide a solution. What's in a Reproducible Example? Parts of a reproducible example: background information - Describe what you are trying to do. What have you already done? complete set up - include any library() calls and data to reproduce your issue. data for a reprex: Here's a discussion on setting up data for a reprex make it run - include the minimal code required to reproduce your error on the data…

Here is an example of what you are after using the iris dataset. You can adapt it to your problem.

library(dplyr)
iris %>% 
  group_by(Species) %>% 
  arrange(Petal.Length) %>% 
  slice(1)

For you, group by the PatientID, then arrange by the date or exam count.