Fix generate_alpha_test_single function: Add default value for adj.vars parameter

- Added adj.vars = NULL as default parameter to prevent missing argument error
- Updated formula construction logic to handle NULL adj.vars properly
- Fixed issue where function would fail when adj.vars was not provided
- All three scenarios now work correctly:
  1. adj.vars not provided (uses default NULL)
  2. adj.vars explicitly set to NULL
  3. adj.vars provided with actual variables
- Tested with quick verification script to ensure functionality

This resolves the same type of issue found in generate_beta_change_test_pair function.

Author: cafferychen777

R/generate_alpha_test_single.R

@@ -68,7 +68,7 @@ generate_alpha_test_single <-
            time.var = NULL,
            t.level = NULL,
            group.var,
-           adj.vars) {
+           adj.vars = NULL) {
 
     if (is.null(alpha.name)){
       return()
@@ -123,10 +123,12 @@ generate_alpha_test_single <-
         )
 
       # Create a formula for lm
+      formula_vars <- group.var
+      if (!is.null(adj.vars)) {
+        formula_vars <- c(adj.vars, group.var)
+      }
       formula <-
-        as.formula(paste0(names(merged_df)[2], "~", paste(c(
-          adj.vars, group.var
-        ), collapse = "+")))
+        as.formula(paste0(names(merged_df)[2], "~", paste(formula_vars, collapse = "+")))
 
       # Run lm and create a coefficient table
       lm.model <- lm(formula, data = merged_df)