init pd df with string instead

app.py

@@ -78,7 +78,7 @@ def prepare_heatmap_data(data):
     print("DEBUG: Data type received in prepare_heatmap_data:", type(data))
     print("DEBUG: Data content:", data)
 
-    heatmap_data = pd.DataFrame(0.0, index=range(len(data)), columns=id2label.values())
+    heatmap_data = pd.DataFrame("", index=range(len(data)), columns=id2label.values())
 
     for idx, row in enumerate(data):
         print(f"DEBUG: Item at index {idx}: {row} (type: {type(row)})")