Fix when all values are the same

Author: NathanBaulch

AsciiChart.Sharp.Tests/Tests.cs

@@ -20,6 +20,8 @@ public void TestPlot(double[] series, Options opts, string expected)
 
         private static object[][] Cases =
         {
+            new object[] { new double[] { 1, 1, 1, 1, 1 }, null, " 1.00 ┼──── " },
+            new object[] { new double[] { 0, 0, 0, 0, 0 }, null, " 0.00 ┼──── " },
             new object[]
             {
                 new double[] { 2, 1, 1, 2, -2, 5, 7, 11, 3, 7, 1 }, null, @"

AsciiChart.Sharp/AsciiChart.cs

@@ -23,7 +23,7 @@ public static string Plot(IEnumerable<double> series, Options options = null)
             var max = seriesList.Max();
 
             var range = Math.Abs(max - min);
-            var ratio = ((options.Height) ?? range) / range;
+            var ratio = range == 0 ? 0 : (options.Height ?? range) / range;
             var min2 = Math.Round(min * ratio, MidpointRounding.AwayFromZero);
             var max2 = Math.Round(max * ratio, MidpointRounding.AwayFromZero);
             var rows = Math.Abs(max2 - min2);
@@ -101,7 +101,7 @@ static IReadOnlyList<double> GetYAxisTicks(double max, double range, double rows
             var yTicks = new List<double>();
             for (var i = 0; i < numberOfTicks; i++)
             {
-                yTicks.Add(max - i * range/rows);
+                yTicks.Add(max - i * (range == rows ? 1 : range/rows));
             }
 
             return yTicks;