Improved stacked graph

lib/domains/charts/models/month_totals.dart

@@ -0,0 +1,29 @@
+class MonthTotals {
+  Map<String, double> positives;
+  Map<String, double> negatives;
+
+  MonthTotals({
+    required this.positives,
+    required this.negatives,
+  });
+
+  double maxValue() {
+    double max = 0.0;
+
+    if (positives.isNotEmpty) {
+      double localMax = positives.values.reduce((value, element) => value + element);
+      if (localMax > max) {
+        max = localMax;
+      }
+    }
+
+    if (negatives.isNotEmpty) {
+      double localMax2 = negatives.values.reduce((value, element) => value + element);
+      if (localMax2 > max) {
+        max = localMax2;
+      }
+    }
+    
+    return max;
+  }
+}