fix: pandas 3.0 compat — use DataFrame.sample() instead of groupby().apply()

app.py

@@ -890,21 +890,11 @@ def chart3(ndim, color_by, filter_type, topn_str, active_data):
         sub["Cluster"] = sub["Cluster"].astype(str)
         color = "Cluster"
 
-    # Stratified subsample for browser performance: cap at MAX_SCATTER points
-    # while preserving the distribution across colour groups.
+    # Subsample for browser performance: cap at MAX_SCATTER points.
     MAX_SCATTER = 30_000
     n_total = len(sub)
     if n_total > MAX_SCATTER:
-        group_col = color if color and color in sub.columns else "Family"
-        sub = (
-            sub.groupby(group_col, observed=True, group_keys=False)
-            .apply(
-                lambda g: g.sample(
-                    max(1, round(MAX_SCATTER * len(g) / n_total)),
-                    random_state=42,
-                )
-            )
-        )
+        sub = sub.sample(MAX_SCATTER, random_state=42)
 
     scatter_title_suffix = (
         f" ({len(sub):,} / {n_total:,})" if n_total > MAX_SCATTER else ""