Plot.PlotFill() #255

dev/changelog.md

@@ -26,6 +26,7 @@ _ScottPlot uses [semantic](https://semver.org/) (major.minor.patch) versioning.
   * Create a SkiaSharp rendering module and user control (supporting OpenGL hardware acceleration)
 
 ## ScottPlot 4.0.29 (in development)
+* `Plot.PlotFill()` can be used to make scatter plots with shaded regions. Giving it a single pair of X/Y values (`xs, ys`) lets you shade beneath the curve to the `baseline` value (which defaults to 0). You can also give it a pair of X/Y values (`xs1, ys1, xs2, ys2`) and the area between the two curves will be shaded (the two curves do not need to be the same length). See cookbook for examples. (#255) _Thanks @ckovamees_ 
 * `DataGen.Range()` now has `includeStop` argument to include the last value in the returned array.
 * `Tools.Pad()` has been created to return a copy of a given array padded with data values on each side. (#255) _Thanks @ckovamees_
 

src/ScottPlot/Plot.cs

@@ -430,6 +430,62 @@ public void Clear(Predicate<Plottable> plottablesToClear)
             return scatterPlot;
         }
 
+        public PlottablePolygon PlotFill(
+            double[] xs,
+            double[] ys,
+            string label = null,
+            double lineWidth = 0,
+            Color? lineColor = null,
+            bool fill = true,
+            Color? fillColor = null,
+            double fillAlpha = 1,
+            double baseline = 0
+            )
+        {
+            if (xs.Length != ys.Length)
+                throw new ArgumentException("xs and ys must all have the same length");
+
+            double[] xs2 = Tools.Pad(xs, cloneEdges: true);
+            double[] ys2 = Tools.Pad(ys, padWithLeft: baseline, padWithRight: baseline);
+
+            return PlotPolygon(xs2, ys2, label, lineWidth, lineColor, fill, fillColor, fillAlpha);
+        }
+
+        public PlottablePolygon PlotFill(
+            double[] xs1,
+            double[] ys1,
+            double[] xs2,
+            double[] ys2,
+            string label = null,
+            double lineWidth = 0,
+            Color? lineColor = null,
+            bool fill = true,
+            Color? fillColor = null,
+            double fillAlpha = 1,
+            double baseline = 0
+            )
+        {
+            if ((xs1.Length != ys1.Length) || (xs2.Length != ys2.Length))
+                throw new ArgumentException("xs and ys for each dataset must have the same length");
+
+            int pointCount = xs1.Length + xs2.Length;
+            double[] bothX = new double[pointCount];
+            double[] bothY = new double[pointCount];
+
+            // copy the first dataset as-is
+            Array.Copy(xs1, 0, bothX, 0, xs1.Length);
+            Array.Copy(ys1, 0, bothY, 0, ys1.Length);
+
+            // copy the second dataset in reverse order
+            for (int i = 0; i < xs2.Length; i++)
+            {
+                bothX[xs1.Length + i] = xs2[xs2.Length - 1 - i];
+                bothY[ys1.Length + i] = ys2[ys2.Length - 1 - i];
+            }
+
+            return PlotPolygon(bothX, bothY, label, lineWidth, lineColor, fill, fillColor, fillAlpha);
+        }
+
         public PlottableFunction PlotFunction(
             Func<double, double?> function,
             Color? color = null,

tests/PlotTypes/Fill.cs

@@ -0,0 +1,88 @@
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+
+namespace ScottPlotTests.PlotTypes
+{
+    public class Fill
+    {
+        [Test]
+        public void Test_Fill_OneCurve()
+        {
+            double[] xs = ScottPlot.DataGen.Range(0, 10, .1, true);
+            double[] ys = ScottPlot.DataGen.Sin(xs);
+
+            var plt = new ScottPlot.Plot(400, 300);
+            plt.PlotFill(xs, ys, fillAlpha: .5);
+            plt.PlotHLine(0, color: Color.Black, lineStyle: ScottPlot.LineStyle.Dash);
+            plt.AxisAuto(0);
+
+            TestTools.SaveFig(plt);
+        }
+
+        [Test]
+        public void Test_Fill_OneCurveWithBaseline()
+        {
+            double[] xs = ScottPlot.DataGen.Range(0, 10, .1, true);
+            double[] ys = ScottPlot.DataGen.Sin(xs);
+
+            var plt = new ScottPlot.Plot(400, 300);
+            plt.PlotFill(xs, ys, fillAlpha: .5, baseline: .5);
+            plt.PlotHLine(0.5, color: Color.Black, lineStyle: ScottPlot.LineStyle.Dash);
+            plt.AxisAuto(0);
+
+            TestTools.SaveFig(plt);
+        }
+
+        [Test]
+        public void Test_Fill_Between()
+        {
+            // the sine wave will have ~100 points
+            double[] xs1 = ScottPlot.DataGen.Range(1, 10, .1, true);
+            double[] ys1 = ScottPlot.DataGen.Sin(xs1);
+
+            // the sine wave will have ~20 points
+            double[] xs2 = ScottPlot.DataGen.Range(1, 10, .5, true);
+            double[] ys2 = ScottPlot.DataGen.Cos(xs2);
+
+            var plt = new ScottPlot.Plot(400, 300);
+            plt.PlotFill(xs1, ys1, xs2, ys2, fillAlpha: .3);
+            plt.PlotScatter(xs1, ys1, Color.Black, 2);
+            plt.PlotScatter(xs2, ys2, Color.Black, 2);
+            plt.AxisAuto(0);
+
+            TestTools.SaveFig(plt);
+        }
+
+        [Test]
+        public void Test_Fill_SeveralCurvesWithLegend()
+        {
+            double[] blueLineXs = { 0, 3, 5.5, 8, 10, 14, 15 };
+            double[] blueLineYs = { 10, 13, 10, 13, 11, 15, 15 };
+
+            double[] greenLineXs = { 0, 5, 6.5, 8, 11, 15 };
+            double[] greenLineYs = { 6, 2, 3.5, 2, 5, 1 };
+
+            double[] redLineXs = { 0, 5, 8, 15 };
+            double[] redLineYs = { 2, 7, 4, 11 };
+
+            var plt = new ScottPlot.Plot(400, 300);
+
+            plt.PlotFill(blueLineXs, blueLineYs,
+                fillColor: Color.Blue, fillAlpha: .5, label: "blue");
+            plt.PlotFill(redLineXs, redLineYs,
+                fillColor: Color.Red, fillAlpha: .5, label: "red");
+            plt.PlotFill(greenLineXs, greenLineYs,
+                fillColor: Color.Green, fillAlpha: .5, label: "green");
+
+            plt.Legend(shadowDirection: ScottPlot.shadowDirection.none);
+
+            plt.AxisAuto(0, 0);
+
+            TestTools.SaveFig(plt);
+        }
+    }
+}