eucast_rules(): add add_if_missing argument to control NA imputation (#259)

When `add_if_missing = FALSE`, rules are only applied to cells that already
contain an SIR value; `NA` cells are left untouched. This is useful with
`overwrite = TRUE` to update reported results without imputing values for
drugs that were not tested.

https://claude.ai/code/session_01Nucc8nXGLqNUjtuC9GrhTc

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: AMR
-Version: 3.0.1.9033
+Version: 3.0.1.9034
 Date: 2026-03-09
 Title: Antimicrobial Resistance Data Analysis
 Description: Functions to simplify and standardise antimicrobial resistance (AMR)

NEWS.md

@@ -1,4 +1,4 @@
-# AMR 3.0.1.9033
+# AMR 3.0.1.9034
 
 ### New
 * Integration with the **tidymodels** framework to allow seamless use of SIR, MIC and disk data in modelling pipelines via `recipes`
@@ -15,6 +15,7 @@
   - Functions such as `susceptibility()` count WT as S and NWT as R
 * `interpretive_rules()`, which allows future implementation of CLSI interpretive rules (#235)
   - `eucast_rules()` has become a wrapper around that function
+* `eucast_rules()` / `interpretive_rules()` gained argument `add_if_missing` (default: `TRUE`). When set to `FALSE`, rules are only applied to cells that already contain an SIR value; `NA` cells are left untouched. This is useful with `overwrite = TRUE` to update reported results without imputing values for drugs that were not tested (#259)
 * Two new `NA` objects, `NA_ab_` and `NA_mo_`, analogous to base R's `NA_character_` and `NA_integer_`, for use in pipelines that require typed missing values
 
 ### Fixes

R/interpretive_rules.R

@@ -79,6 +79,7 @@ format_eucast_version_nr <- function(version, markdown = TRUE) {
 #' @param only_sir_columns A [logical] to indicate whether only antimicrobial columns must be included that were transformed to class [sir][as.sir()] on beforehand. Defaults to `FALSE` if no columns of `x` have a class [sir][as.sir()].
 #' @param custom_rules Custom rules to apply, created with [custom_eucast_rules()].
 #' @param overwrite A [logical] indicating whether to overwrite existing SIR values (default: `FALSE`). When `FALSE`, only non-SIR values are modified (i.e., any value that is not already S, I or R). To ensure compliance with EUCAST guidelines, **this should remain** `FALSE`, as EUCAST notes often state that an organism "should be tested for susceptibility to individual agents or be reported resistant".
+#' @param add_if_missing A [logical] indicating whether rules should also be applied to missing (`NA`) values (default: `TRUE`). When `FALSE`, rules are only applied to cells that already contain an SIR value; cells with `NA` are left untouched. This is particularly useful when using `overwrite = TRUE` with custom rules and you want to update reported results without imputing values for untested drugs.
 #' @inheritParams first_isolate
 #' @details
 #' **Note:** This function does not translate MIC values to SIR values. Use [as.sir()] for that. \cr
@@ -175,6 +176,7 @@ interpretive_rules <- function(x,
                                only_sir_columns = any(is.sir(x)),
                                custom_rules = NULL,
                                overwrite = FALSE,
+                               add_if_missing = TRUE,
                                ...) {
   meet_criteria(x, allow_class = "data.frame")
   meet_criteria(col_mo, allow_class = "character", has_length = 1, is_in = colnames(x), allow_NULL = TRUE)
@@ -189,6 +191,7 @@ interpretive_rules <- function(x,
   meet_criteria(only_sir_columns, allow_class = "logical", has_length = 1)
   meet_criteria(custom_rules, allow_class = "custom_eucast_rules", allow_NULL = TRUE)
   meet_criteria(overwrite, allow_class = "logical", has_length = 1)
+  meet_criteria(add_if_missing, allow_class = "logical", has_length = 1)
 
   stop_if(
     guideline == "CLSI",
@@ -538,7 +541,8 @@ interpretive_rules <- function(x,
           warned = warned,
           info = info,
           verbose = verbose,
-          overwrite = overwrite
+          overwrite = overwrite,
+          add_if_missing = add_if_missing
         )
         n_added <- n_added + run_changes$added
         n_changed <- n_changed + run_changes$changed
@@ -580,7 +584,8 @@ interpretive_rules <- function(x,
           warned = warned,
           info = info,
           verbose = verbose,
-          overwrite = overwrite
+          overwrite = overwrite,
+          add_if_missing = add_if_missing
         )
         n_added <- n_added + run_changes$added
         n_changed <- n_changed + run_changes$changed
@@ -877,7 +882,8 @@ interpretive_rules <- function(x,
       warned = warned,
       info = info,
       verbose = verbose,
-      overwrite = overwrite
+      overwrite = overwrite,
+      add_if_missing = add_if_missing
     )
     n_added <- n_added + run_changes$added
     n_changed <- n_changed + run_changes$changed
@@ -947,7 +953,8 @@ interpretive_rules <- function(x,
         warned = warned,
         info = info,
         verbose = verbose,
-        overwrite = overwrite
+        overwrite = overwrite,
+        add_if_missing = add_if_missing
       )
       n_added <- n_added + run_changes$added
       n_changed <- n_changed + run_changes$changed
@@ -1139,7 +1146,8 @@ edit_sir <- function(x,
                      warned,
                      info,
                      verbose,
-                     overwrite) {
+                     overwrite,
+                     add_if_missing) {
   cols <- unique(cols[!is.na(cols) & !is.null(cols)])
 
   # for Verbose Mode, keep track of all changes and return them
@@ -1172,13 +1180,15 @@ edit_sir <- function(x,
     if (isFALSE(overwrite) && any(isSIR) && message_not_thrown_before("edit_sir.warning_overwrite")) {
       warning_("Some values had SIR values and were not overwritten, since `overwrite = FALSE`.")
     }
+    # determine which cells to modify based on overwrite and add_if_missing
+    apply_mask <- if (isTRUE(overwrite)) {
+      if (isFALSE(add_if_missing)) !isNA else rep(TRUE, length(isNA))
+    } else {
+      if (isFALSE(add_if_missing)) isSIR else non_SIR
+    }
     tryCatch(
       # insert into original table
-      if (isTRUE(overwrite)) {
+      new_edits[rows, cols][apply_mask] <- to,
-        new_edits[rows, cols] <- to
-      } else {
-        new_edits[rows, cols][non_SIR] <- to
-      },
       warning = function(w) {
         if (w$message %like% "invalid factor level") {
           xyz <- vapply(FUN.VALUE = logical(1), cols, function(col) {
@@ -1188,11 +1198,7 @@ edit_sir <- function(x,
             )
             TRUE
           })
-          if (isTRUE(overwrite)) {
+          suppressWarnings(new_edits[rows, cols][apply_mask] <<- to)
-            suppressWarnings(new_edits[rows, cols] <<- to)
-          } else {
-            suppressWarnings(new_edits[rows, cols][non_SIR] <<- to)
-          }
           warning_(
             "in `eucast_rules()`: value \"", to, "\" added to the factor levels of column",
             ifelse(length(cols) == 1, "", "s"),