How to define/customize Legend for a chart?

[kunjiangkun]

In version 5.0, legend is no longer an option for Layout.init. The legend option is also not exposed for trace such as Chart2D.Scatter. Looking at the code, it's defined for inner function Trace2DStyle.Scatter but Legend arg is set to null. Please provide an example for customizing Legend.

[kunjiangkun]

Somehow chart.WithLegend only supports arg of bool. Have to call GenericChartExtensions.WithLegend(trace, legendSetting) explicitly to get it working.

var boxPlot = box
.WithLegend(true)
.WithXAxis(xAxis)
.WithLayout(plotLayout)
.WithSize(plotWidth, plotHeight);
GenericChartExtensions.WithLegend(boxPlot, legendSetting);

[kMutagene]

It is hard for me to make out the problem because you are mixing some concepts here. Chart2D.Scatter does not create a trace - it creates a GenericChart which contains trace(s), a layout, a config, and display options. The reason is that plotly strictly separates the layout of a chart from traces. Traces are just the data and style options of a single trace (e.g., the marker style). Layout options on the other hand are styling options for the whole chart, no matter how many traces it has. A legend is exactly such an object - something that is displayed for one or more traces of the chart.

So you are always aiming to set the legend on the layout, or use a method that changes the layout part of a GenericChart, for which you have multiple options:

• F# core API (these return F# functions, which you'd need to call Invoke on from C#):

  • Layout.setLegend or Layout.updateLegendById - static methods on the Layout class:

    Plotly.NET/src/Plotly.NET/Layout/Layout.fs

    Line 1126 in 98a4d18

    static member setLegend(id: StyleParam.SubPlotId, legend: Legend) =

  • Chart.withLegend or Chart.withLegendStyle - static methods of the Chart API:

    Plotly.NET/src/Plotly.NET/ChartAPI/Chart.fs

    Line 2629 in 98a4d18

    static member withLegend(legend: Legend, [<Optional; DefaultParameterValue(null)>] ?Id: int) =

  • GenericChartExtensions provides multiple overloads, one of them only takes boolean and needs to be removed, but there are others as well, see here :

    Plotly.NET/src/Plotly.NET/CSharpLayer/GenericChartExtensions.fs

    Lines 610 to 613 in 98a4d18

    	// Set the LayoutGrid options of a Chart
    	[<CompiledName("WithLegend")>]
    	member this.WithLegend(legend: Legend, [<Optional; DefaultParameterValue(null)>] ?Id: int) =
    	this |> Chart.withLegend (legend, ?Id = Id)

• GenericChartExtensions in Plotly.NET.C#:

  • WithLegend or WithLegendStyle:

    Plotly.NET/src/Plotly.NET.CSharp/GenericChartExtensions.cs

    Line 377 in 98a4d18

    public static GenericChart WithLegend(