mpg chart grace revisited.

Author: hargata

Helper/StaticHelper.cs

@@ -855,5 +855,19 @@ public static byte[] RemindersToCalendar(List<ReminderRecordViewModel> reminders
             string calendarContent = sb.ToString();
             return Encoding.UTF8.GetBytes(calendarContent);
         }
+        public static decimal CalculateNiceStepSize(decimal min, decimal max, int desiredTicks)
+        {
+            double range = Convert.ToDouble(max - min);
+            double roughStep = range / desiredTicks;
+            double exponent = Math.Floor(Math.Log10(roughStep));
+            double stepPower = Math.Pow(10, exponent);
+            double normalizedStep = roughStep / stepPower;
+
+            // Choose the closest nice interval (1, 2, or 5)
+            double[] niceSteps = { 1, 2, 5 };
+            double goodNormalizedStep = niceSteps.OrderBy(s => Math.Abs(s - normalizedStep)).First();
+
+            return Convert.ToDecimal(goodNormalizedStep * stepPower);
+        }
     }
 }

Views/Vehicle/_MPGByMonthReport.cshtml

@@ -6,15 +6,30 @@
     var barGraphColors = StaticHelper.GetBarChartColors();
     var userConfig = config.GetUserConfig(User);
     var userLanguage = userConfig.UserLanguage;
-
+}
+@if (Model.CostData.Any(x => x.Cost > 0))
+{
+    var chartMax = Math.Ceiling(Model.CostData.Max(x => x.Cost));
     var graphGrace = Decimal.ToInt32(Model.CostData.Max(x => x.Cost) - Model.CostData.Min(x => x.Cost));
-    if (graphGrace < 0 || Model.CostData.Min(x=>x.Cost) - graphGrace < 0)
+    var chartMin = Math.Floor(Model.CostData.Min(x => x.Cost) - graphGrace);
+    if (graphGrace < 0 || chartMin < 0)
     {
         graphGrace = 0;
+        chartMin = 0;
+    }
+    var stepSize = StaticHelper.CalculateNiceStepSize(chartMin, chartMax, 8);
+    var remMin = stepSize > 0 ? chartMin % stepSize : 0;
+    var cleanedMin = chartMin - remMin;
+    if (remMin >= (stepSize / 2))
+    {
+        cleanedMin += stepSize;
+    }
+    var remMax = stepSize > 0 ? chartMax % stepSize : 0;
+    var cleanedMax = chartMax - remMax;
+    if (remMax >= (stepSize / 2))
+    {
+        cleanedMax += stepSize;
     }
-}
-@if (Model.CostData.Any(x => x.Cost > 0))
-{
     <canvas id="bar-chart-mpg"></canvas>
     <script>
         renderChart();
@@ -60,9 +75,11 @@
                         scales: {
                             y: {
                                 beginAtZero: false,
-                                grace: decodeHTMLEntities('@(graphGrace)'),
+                                max: Math.ceil(decodeHTMLEntities('@(cleanedMax)')),
+                                min: Math.floor(decodeHTMLEntities('@(cleanedMin)')),
                                 ticks: {
-                                    color: useDarkMode ? "#fff" : "#000"
+                                    color: useDarkMode ? "#fff" : "#000",
+                                    stepSize: Math.ceil(decodeHTMLEntities('@(stepSize)'))
                                 }
                             },
                             x: {