Calculate percentage of usage for selected codes

[milanwiedemann]

This is just an example how to calculate the percentage of code usage for selected codes. The main additions are:

1. The calculation in server.R:

   group_by(code, description) |>
   summarise(total_usage = sum(usage, na.rm = TRUE)) |>
   ungroup() |>
   mutate(total_pct = total_usage / sum(total_usage, na.rm = TRUE)) |>
   arrange(desc(total_usage))

2. Changes to the table formatting in tables.R:

   formatPercentage(
     "total_pct",
     digits = 3
   )

Note that in cases where a code has slightly different descriptions across the years this will show each unique code and description pair separately but I think that's acceptable. For example code SNOMED-CD code 103069003 had three slightly different descriptions over the years:

  start_date end_date   snomed_concept_id description                                       
  <date>     <date>     <chr>             <chr>        
1 2023-08-01 2024-07-31 103069003         Vitamin B and/or vitamin B derivative (substance)          
2 2022-08-01 2023-07-31 103069003         Vitamin B and/or vitamin B derivative (substance)         
3 2020-08-01 2021-07-31 103069003         Vitamin B and vitamin B derivative (substance)          
4 2019-08-01 2020-07-31 103069003         Vitamin B (substance)