support groups for portion_df, update README

tests/testthat/test-ggplot_rsi.R

@@ -32,4 +32,13 @@ test_that("ggplot_rsi works", {
   expect_error(geom_rsi(x = "test"))
   expect_error(facet_rsi(facet = "test"))
 
+  # support for groups
+  print(
+    septic_patients %>%
+      select(hospital_id, amox, cipr) %>%
+      group_by(hospital_id) %>%
+      ggplot_rsi() +
+      facet_grid("hospital_id")
+  )
+
 })