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FabianNitscheVisualMelon
FabianNitsche
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VisualMelon
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Fix for logarithmic axis for LinearBarSeries (#740) (#1942)
* Add demo for LinearBarSeries with logarithmic axis. * Fix for logarithmic LinearBarSeries. * Fix for padding calculation for logarithmic axis. * Updated Changelog. * Use BaseLine and LowestValidRoundTripValue on LogarithmicAxis to render LineBarSeries correctly. * Better separated box generation from zoom. --------- Co-authored-by: VisualMelon <VisualMelon@users.noreply.github.com>
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Lines changed: 151 additions & 5 deletions

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‎CHANGELOG.md‎

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@@ -47,6 +47,7 @@ All notable changes to this project will be documented in this file.
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- CategoryAxis.ItemsSource without BarSeries (#1847)
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- Histogram now rendering properly when using logarithmic Y axis (#740)
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- Fix ExampleLibrary build errors in certain code pages (#1890)
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- LineBarSeries now rendering properly when using logarithmic scale (#740)
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- Fix for double.Epsilon zero check that fails on some architectures (#1924)
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## [2.1.0] - 2021-10-02

‎Source/Examples/ExampleLibrary/Series/LinearBarSeriesExamples.cs‎

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@@ -44,9 +44,20 @@ public static PlotModel WithStroke()
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[Example("With negative colors")]
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public static PlotModel WithNegativeColors()
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{
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var model = new PlotModel { Title = "LinearBarSeries with stroke" };
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return CreateWithNegativeColors();
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}
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[Example("With negative colors (logaritmic)")]
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public static PlotModel WithNegativeColorsLogarithmic()
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{
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return CreateWithNegativeColors(true);
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}
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public static PlotModel CreateWithNegativeColors(bool logarithmic = false)
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{
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var model = new PlotModel { Title = logarithmic ? "LinearBarSeries with stroke (logarithmic)" : "LinearBarSeries with stroke" };
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model.Axes.Add(new LinearAxis { Position = AxisPosition.Bottom });
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model.Axes.Add(new LinearAxis { Position = AxisPosition.Left });
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model.Axes.Add(logarithmic ? (Axis)new LogarithmicAxis { Position = AxisPosition.Left } : new LinearAxis { Position = AxisPosition.Left });
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var linearBarSeries = CreateExampleLinearBarSeriesWithNegativeValues();
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linearBarSeries.Title = "LinearBarSeries";
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linearBarSeries.FillColor = OxyColor.Parse("#454CAF50");

‎Source/OxyPlot/Axes/LogarithmicAxis.cs‎

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@@ -20,6 +20,12 @@ namespace OxyPlot.Axes
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/// <see href="http://en.wikipedia.org/wiki/Logarithmic_scale"/>
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public class LogarithmicAxis : Axis
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{
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/// <summary>
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/// The lowest value that can be transformed to logarithmic and
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/// back yielding the same non-infinite number.
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/// </summary>
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public static readonly double LowestValidRoundtripValue = 2.22507385850726E-308;
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/// <summary>
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/// Initializes a new instance of the <see cref = "LogarithmicAxis" /> class.
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/// </summary>
@@ -633,5 +639,86 @@ protected override void CoerceActualMaxMin()
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base.CoerceActualMaxMin();
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}
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/// <summary>
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/// Calculates the actual maximum value of the axis, including the <see cref="Axis.MaximumPadding" />.
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/// </summary>
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/// <returns>The new actual maximum value of the axis.</returns>
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/// <remarks>
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/// Must be called before <see cref="CalculateActualMinimum" />
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/// </remarks>
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protected override double CalculateActualMaximum()
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{
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var actualMaximum = this.DataMaximum;
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double range = this.DataMaximum - this.DataMinimum;
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if (range < double.Epsilon)
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{
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double zeroRange = this.DataMaximum > 0 ? this.DataMaximum : 1;
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actualMaximum += zeroRange * 0.5;
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}
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if (!double.IsNaN(this.DataMinimum) && !double.IsNaN(actualMaximum))
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{
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// On log axis we actually see log(x). Now if we want to have a padding we need to change actualMaximum
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// to an x value that corresponds to the padding expected in log scale
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// x_0 x_1 x_2
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// |---------------------|--------|
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// log(x_0) log(x_1) log(x_2)
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// where actualMaximum = x_2
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//
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// log(x_2) - log(x_1) = padding * [log(x_1) - log(x_0)]
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// log(x_2) = padding * log(x_1/x_0) + log(x_1)
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// x_2 = (x_1/x_0)^padding * x_1
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double x1 = actualMaximum;
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double x0 = this.DataMinimum;
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return Math.Pow(x1, this.MaximumPadding + 1) * (x0 > double.Epsilon ? Math.Pow(x0, -this.MaximumPadding) : 1);
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}
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return actualMaximum;
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}
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/// <summary>
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/// Calculates the actual minimum value of the axis, including the <see cref="Axis.MinimumPadding" />.
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/// </summary>
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/// <returns>The new actual minimum value of the axis.</returns>
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/// <remarks>
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/// Must be called after <see cref="CalculateActualMaximum" />
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/// </remarks>
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protected override double CalculateActualMinimum()
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{
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var actualMinimum = this.DataMinimum;
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double range = this.DataMaximum - this.DataMinimum;
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if (range < double.Epsilon)
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{
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double zeroRange = this.DataMaximum > 0 ? this.DataMaximum : 1;
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actualMinimum -= zeroRange * 0.5;
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}
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if (!double.IsNaN(this.ActualMaximum))
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{
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// For the padding on the min value it is very similar to the calculation mentioned in
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// CalculateActualMaximum. However, since this is called after CalculateActualMaximum,
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// we no longer know x_1.
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// x_3 x_0 x_1 x_2
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// |---------|------------|--------|
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// log(x_3) log(x_0) log(x_1) log(x_2)
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// where actualMiminum = x_3
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// log(x_0) - log(x_3) = padding * [log(x_1) - log(x_0)]
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// from CalculateActualMaximum we can use
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// log(x_1) = [log(x_2) + max_padding * log(x_0)] / (1 + max_padding)
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// x_3 = x_0^[1 + padding - padding * max_padding / (1 + max_padding)] * x_2^[-padding / (1 + max_padding)]
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double x1 = this.ActualMaximum;
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double x0 = actualMinimum;
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double existingPadding = this.MaximumPadding;
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return Math.Pow(x0, 1 + this.MinimumPadding - this.MinimumPadding * existingPadding / (1 + existingPadding)) * Math.Pow(x1, -this.MinimumPadding / (1 + existingPadding));
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}
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return actualMinimum;
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}
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}
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}

‎Source/OxyPlot/Series/BarSeries/BarSeries.cs‎

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@@ -9,6 +9,7 @@
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namespace OxyPlot.Series
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{
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using OxyPlot.Axes;
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using System;
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using System.Collections.Generic;
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using System.Linq;
@@ -46,7 +47,7 @@ public BarSeries()
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/// </summary>
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/// <value>The actual color.</value>
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public OxyColor ActualFillColor => this.FillColor.GetActualColor(this.defaultFillColor);
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/// <summary>
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/// Gets or sets the base value.
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/// </summary>
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var topValue = this.IsStacked ? baseValue + value : value;
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if (this.YAxis.IsLogarithmic() && !this.YAxis.IsValidValue(topValue))
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{
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continue;
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}
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// Calculate offset
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double categoryValue;
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if (this.IsStacked)
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this.Manager.SetCurrentBaseValue(stackIndex, categoryIndex, value < 0, topValue);
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}
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if (this.YAxis.IsLogarithmic() && !this.YAxis.IsValidValue(baseValue))
413+
{
414+
baseValue = LogarithmicAxis.LowestValidRoundtripValue;
415+
}
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var rect = new OxyRect(this.Transform(baseValue, categoryValue), this.Transform(topValue, categoryValue + actualBarWidth));
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this.ActualBarRectangles.Add(rect);

‎Source/OxyPlot/Series/BarSeries/LinearBarSeries.cs‎

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@@ -9,7 +9,10 @@
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namespace OxyPlot.Series
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{
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using OxyPlot.Axes;
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using System;
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using System.Collections.Generic;
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using System.Linq;
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/// <summary>
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/// Represents a series to display bars in a linear axis
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}
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}
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/// <summary>
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/// Gets or sets the base line. This value is used for plotting to determine
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/// the start of the plot. A suitable value is selected automatically if it is NaN.
102+
/// </summary>
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public double BaseLine { get; set; } = double.NaN;
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/// <summary>
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/// Gets the nearest point.
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/// </summary>
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195204
{
196205
base.UpdateAxisMaxMin();
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198-
this.YAxis.Include(0.0);
207+
this.YAxis.Include(this.GetBaseLineOrAutomaticValue(this.YAxis));
208+
}
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210+
/// <summary>
211+
/// Gets the base line value. If the value of the property is NaN, a sensible value is returned.
212+
/// </summary>
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/// <param name="axis">The axis for which to return a sensible value for.</param>
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/// <returns>The base line property or a sensible default.</returns>
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protected double GetBaseLineOrAutomaticValue(Axis axis)
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{
217+
if (double.IsNaN(this.BaseLine))
218+
{
219+
if (axis.IsLogarithmic())
220+
{
221+
var lowestPostiveY = this.ActualPoints == null ? 1 : this.ActualPoints.Select(p => p.Y).Where(y => y > 0).Min();
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return Math.Sqrt(lowestPostiveY);
223+
}
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return 0;
225+
}
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return this.BaseLine;
199228
}
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201230
/// <summary>
@@ -265,7 +294,7 @@ private void RenderBars(IRenderContext rc, List<DataPoint> actualPoints)
265294
}
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267296
var screenPoint = this.Transform(actualPoint) - widthVector;
268-
var basePoint = this.Transform(new DataPoint(actualPoint.X, 0)) + widthVector;
297+
var basePoint = this.Transform(new DataPoint(actualPoint.X, this.GetBasePointY())) + widthVector;
269298
var rectangle = new OxyRect(basePoint, screenPoint);
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this.rectangles.Add(rectangle);
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this.rectanglesPointIndexes.Add(pointIndex);
@@ -281,6 +310,13 @@ private void RenderBars(IRenderContext rc, List<DataPoint> actualPoints)
281310
}
282311
}
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313+
private double GetBasePointY()
314+
{
315+
if (this.YAxis.IsLogarithmic())
316+
return LogarithmicAxis.LowestValidRoundtripValue;
317+
return 0;
318+
}
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/// <summary>
285321
/// Computes the bars width.
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/// </summary>

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