Empty Points

• Dec 14, 2022
• 10 minutes to read

Empty points are points with undefined Values. This document describes how the Chart Control processes empty points.

Run Demo: Empty Points

The Chart displays empty points as breaks in the Line or Area series views, and missing points or bars in other series view types.

Line View

Spline Area View

Step Line 3D View

Bar View

Point View

The following table contains data for the charts above:

Date	Politics	Entertainment	Travel
01-Nov-16	65	56	45
02-Nov-16	78	45	40
03-Nov-16	95	70	56
04-Nov-16	110	82	47
05-Nov-16	108	80	38
06-Nov-16	52	20	31
07-Nov-16	46	10	27
08-Nov-16	70		27
09-Nov-16	86		42
10-Nov-16	92	65
11-Nov-16	108	45	37
12-Nov-16	115	56	21
13-Nov-16	75	10	10
14-Nov-16	65	0	5

To create an empty point, execute one of the following actions:

• Leave a point’s value blank if you use the Chart Designer to add points to a series.

  

• Use the SeriesPoint‘s class constructors that take only an argument as a parameter if you add points to a series in code.

  C#

  using DevExpress.XtraCharts;
  using System;
  using System.Collections.Generic;
  using System.Windows.Forms;
  namespace EmptyPointRepresentation {
      public partial class Form1 : Form {
          ChartControl chart { get { return chartControl1; } }
          public Form1() {
              InitializeComponent();
              Series series = new Series();
              // The following line adds an empty series point to a series.
              series.Points.Add(new SeriesPoint(new DateTime(2019,1,1)));
              chart.Series.Add(series);
          }
      }
  }
  

  VB.NET

  Imports DevExpress.XtraCharts
  Imports System
  Imports System.Collections.Generic
  Imports System.Windows.Forms
  Namespace EmptyPointRepresentation
      Public Partial Class Form1
          Inherits Form
  
          Private ReadOnly Property chart As ChartControl
              Get
                  Return chartControl1
              End Get
          End Property
          Public Sub New()
              InitializeComponent()
              Dim series As Series = New Series()
              series.Points.Add(New SeriesPoint(New DateTime(2019, 1, 1)))
              chart.Series.Add(series)
          End Sub
      End Class
  End Namespace
  

• Set a data point’s value to Double.NaN in a data source.

  C#

  using DevExpress.XtraCharts;
  using System;
  using System.Collections.Generic;
  using System.Windows.Forms;
  
  namespace EmptyPointRepresentation {
      public partial class Form1 : Form {
          ChartControl chart { get { return chartControl1; } }
          public Form1() {
              InitializeComponent();
          }
          private void OnFormLoad(object sender, EventArgs e) {
              chart.DataSource = DataPoint.GetPoints();
              Series series1 = new Series("Politics", ViewType.Line);
              series1.SetDataMembers("Date", "Politics");
              Series series2 = new Series("Entertainment", ViewType.Line);
              series2.SetDataMembers("Date", "Entertainment");
              Series series3 = new Series("Travel", ViewType.Line);
              series3.SetDataMembers("Date", "Travel");
              chart.Series.AddRange(new Series[] { series1, series2, series3 });
          }
      }
      public class DataPoint {
          public DateTime Date { get; set; }
          public Double Politics { get; set; }
          public Double Entertainment { get; set; }
          public Double Travel { get; set; }
          public static List<DataPoint> GetPoints() {
              return new List<DataPoint> {
                      new DataPoint { Date = new DateTime(2016,11,1), Politics = 65,   Entertainment = 56, Travel = 45 },
                      new DataPoint { Date = new DateTime(2016,11,2), Politics = 78,   Entertainment = 45, Travel = 40 },
                      new DataPoint { Date = new DateTime(2016,11,3), Politics = 95,   Entertainment = 70, Travel = 56 },
                      new DataPoint { Date = new DateTime(2016,11,4), Politics = 110,  Entertainment = 82, Travel = 47 },
                      new DataPoint { Date = new DateTime(2016,11,5), Politics = 108,  Entertainment = 80, Travel = 38 },
                      new DataPoint { Date = new DateTime(2016,11,6), Politics = 52,   Entertainment = 20, Travel = 31 },
                      new DataPoint { Date = new DateTime(2016,11,7), Politics = 46,   Entertainment = 10, Travel = 27 },
                      new DataPoint { Date = new DateTime(2016,11,8), Politics = 70,   Entertainment = Double.NaN, Travel = 27 },
                      new DataPoint { Date = new DateTime(2016,11,9), Politics = 86,   Entertainment = Double.NaN, Travel = 42 },
                      new DataPoint { Date = new DateTime(2016,11,10), Politics = 92,  Entertainment = 65, Travel = Double.NaN},
                      new DataPoint { Date = new DateTime(2016,11,11), Politics = 105, Entertainment = 45, Travel = 37 },
                      new DataPoint { Date = new DateTime(2016,11,12), Politics = 115, Entertainment = 56, Travel = 21 },
                      new DataPoint { Date = new DateTime(2016,11,13), Politics = 75,  Entertainment = 10, Travel = 10 },
                      new DataPoint { Date = new DateTime(2016,11,14), Politics = 65,  Entertainment = 0 , Travel = 5  }
                  };
          }
      }
  }
  

  VB.NET

  Imports DevExpress.XtraCharts
  Imports System
  Imports System.Collections.Generic
  Imports System.Windows.Forms
  
  Namespace EmptyPointRepresentation
      Public Partial Class Form1
          Inherits Form
  
          Private ReadOnly Property chart As ChartControl
              Get
                  Return chartControl1
              End Get
          End Property
  
          Public Sub New()
              InitializeComponent()
          End Sub
  
          Private Sub OnFormLoad(ByVal sender As Object, ByVal e As EventArgs)
              chart.DataSource = DataPoint.GetPoints()
              Dim series1 As Series = New Series("Politics", ViewType.Line)
              series1.SetDataMembers("Date", "Politics")
              Dim series2 As Series = New Series("Entertainment", ViewType.Line)
              series2.SetDataMembers("Date", "Entertainment")
              Dim series3 As Series = New Series("Travel", ViewType.Line)
              series3.SetDataMembers("Date", "Travel")
              chart.Series.AddRange(New Series() {series1, series2, series3})
          End Sub
      End Class
  
      Public Class DataPoint
          Public Property Date As DateTime
          Public Property Politics As Double
          Public Property Entertainment As Double
          Public Property Travel As Double
  
          Public Shared Function GetPoints() As List(Of DataPoint)
              Return New List(Of DataPoint) From {
                  New DataPoint With { .Date = New DateTime(2016, 11, 1), .Politics = 65,  .Entertainment = 56, .Travel = 45 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 2), .Politics = 78,  .Entertainment = 45, .Travel = 40 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 3), .Politics = 95,  .Entertainment = 70, .Travel = 56 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 4), .Politics = 110, .Entertainment = 82, .Travel = 47 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 5), .Politics = 108, .Entertainment = 80, .Travel = 38 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 6), .Politics = 52,  .Entertainment = 20, .Travel = 31 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 7), .Politics = 46,  .Entertainment = 10, .Travel = 27 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 8), .Politics = 70,  .Entertainment = Double.NaN, .Travel = 27 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 9), .Politics = 86,  .Entertainment = Double.NaN, .Travel = 42 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 10),.Politics = 92,  .Entertainment = 65, .Travel = Double.NaN },
                  New DataPoint With { .Date = New DateTime(2016, 11, 11),.Politics = 105, .Entertainment = 45, .Travel = 37 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 12),.Politics = 115, .Entertainment = 56, .Travel = 21 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 13),.Politics = 75,  .Entertainment = 10, .Travel = 10 },
                  New DataPoint With { .Date = New DateTime(2016, 11, 14),.Politics = 65,  .Entertainment = 0, .Travel = 5 }
              }
          End Function
      End Class
  End Namespace
  

You can use the SeriesPoint.IsEmpty property to check whether a point is empty.

Tip

• You can use scale breaks to hide specific data ranges from an axis.
• To limit data displayed in a chart, configure visual and whole axis ranges.
• If you use an argument axis with a date-time scale, you can exclude holidays, weekends, or specified hours from a scale. Refer to the following help topic for more information: Work Time and Workday Configuration.

Define How to Handle Empty Points

Use a series view’s EmptyPointOptions property to access empty point settings. Specify the EmptyPointOptions.ProcessPoints property to select the manner in which the chart control should handle empty points.

For example, use the following code to display points with predicted values instead of empty points.

C#

using DevExpress.XtraCharts;

    public Form1() {
        InitializeComponent();        
        //...
        BarSeriesView view = (BarSeriesView)series.View;
        EmptyPointOptions emptyPointOptions = view.EmptyPointOptions;
        emptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate;
    }

VB.NET

Imports DevExpress.XtraCharts

    Public Sub New()
        InitializeComponent()
        '...
        Dim view As BarSeriesView = CType(series.View, BarSeriesView)
        Dim emptyPointOptions As EmptyPointOptions = view.EmptyPointOptions
        emptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate
    End Sub

Customize Appearance of Empty Points

Appearance settings of empty points depends on the series view type. Depending on the view, cast the EmptyPointOptions property value to one of the following classes and configure empty point appearance settings:

• EmptyPointOptions – Contains common empty point settings and can be used for all series views.
• LineEmptyPointOptions – Contains settings specific to line series views (for example, LineStyle).
• AreaEmptyPointOptions – Contains settings specific to area series views (for example, FillStyle).

The example below configures empty point appearance for line, area, and bar series views. Empty points are painted gray:

C#

LineSeriesView view1 = (LineSeriesView)series1.View;
view1.MarkerVisibility = DevExpress.Utils.DefaultBoolean.True;
LineEmptyPointOptions lineEmptyPointOptions = view1.EmptyPointOptions;
lineEmptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate;
lineEmptyPointOptions.Color = Color.DarkGray;
lineEmptyPointOptions.LineStyle.DashStyle = DashStyle.Dash;
lineEmptyPointOptions.LineStyle.Thickness = 2;

AreaSeriesView view2 = (AreaSeriesView)series2.View;
AreaEmptyPointOptions areaEmptyPointOptions = view2.EmptyPointOptions;
areaEmptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate;
areaEmptyPointOptions.FillStyle.FillMode = FillMode.Solid;
areaEmptyPointOptions.Color = Color.DarkGray;
areaEmptyPointOptions.Border.Color = Color.Gray;
areaEmptyPointOptions.Border.Thickness = 2;

SideBySideBarSeriesView view3 = (SideBySideBarSeriesView)series3.View;
EmptyPointOptions emptyPointOptions = view3.EmptyPointOptions;
emptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate;
emptyPointOptions.Color = Color.FromArgb(100, Color.DarkGray);

VB.NET

Dim view1 As LineSeriesView = CType(series1.View, LineSeriesView)
view1.MarkerVisibility = DevExpress.Utils.DefaultBoolean.True
Dim lineEmptyPointOptions As LineEmptyPointOptions = view1.EmptyPointOptions
lineEmptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate
lineEmptyPointOptions.Color = Color.DarkGray
lineEmptyPointOptions.LineStyle.DashStyle = DashStyle.Dash
lineEmptyPointOptions.LineStyle.Thickness = 2

Dim view2 As AreaSeriesView = CType(series2.View, AreaSeriesView)
Dim areaEmptyPointOptions As AreaEmptyPointOptions = view2.EmptyPointOptions
areaEmptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate
areaEmptyPointOptions.FillStyle.FillMode = FillMode.Solid
areaEmptyPointOptions.Color = Color.DarkGray
areaEmptyPointOptions.Border.Color = Color.Gray
areaEmptyPointOptions.Border.Thickness = 2

Dim view3 As SideBySideBarSeriesView = CType(series3.View, SideBySideBarSeriesView)
Dim emptyPointOptions As EmptyPointOptions = view3.EmptyPointOptions
emptyPointOptions.ProcessPoints = ProcessEmptyPointsMode.Interpolate
emptyPointOptions.Color = Color.FromArgb(100, Color.DarkGray)

Show Isolated Points

The Chart does not draw a point between two empty points. To display a point in this case, enable the ShowIsolatedPoints property.

ShowIsolatedPoints = true	ShowIsolatedPoints = false

C#

LineSeriesView view = chart.Series[0].View as LineSeriesView;
view.ShowIsolatedPoints = true;

VB.NET

Dim view As LineSeriesView = TryCast(chart.Series(0).View, LineSeriesView)
view.ShowIsolatedPoints = True

Empty Points Specifics

• The Chart Control does not display series labels, tooltips, and the crosshair cursor label for empty points.
• If a data source contains missing records in arguments, data points are not created. Set the ScaleOptionsBase.ProcessMissingPoints property to InsertEmptyPoints to handle missing points as empty points.

• Empty points are ignored when you aggregate Chart’s data and the chart contains data next to empty points within the specified interval of the measurement unit.

  For example, the following list of data points is used as a chart data source:

      public static List<DataPoint> GetPoints() {
          return new List<DataPoint> {
              new DataPoint { Date = new DateTime(2016,11,1), Politics = 65,   Entertainment = 56 },
              new DataPoint { Date = new DateTime(2016,11,2), Politics = 78,   Entertainment = 45 },
              new DataPoint { Date = new DateTime(2016,11,3), Politics = 95,   Entertainment = 70 },
              new DataPoint { Date = new DateTime(2016,11,4), Politics = 110,  Entertainment = 82 },
              new DataPoint { Date = new DateTime(2016,11,5), Politics = 108,  Entertainment = 80 },
              new DataPoint { Date = new DateTime(2016,10,6), Politics = 52,   Entertainment = 20 },
              new DataPoint { Date = new DateTime(2016,10,7), Politics = 46,   Entertainment = 10 },
              new DataPoint { Date = new DateTime(2016,12,8), Politics = 70,   Entertainment = Double.NaN },
              new DataPoint { Date = new DateTime(2017,05,9), Politics = 86,   Entertainment = Double.NaN },
              new DataPoint { Date = new DateTime(2017,05,10), Politics = 92,  Entertainment = 65 },
              new DataPoint { Date = new DateTime(2017,05,11), Politics = 105, Entertainment = 45 },
              new DataPoint { Date = new DateTime(2017,12,12), Politics = 115, Entertainment = 56 },
              new DataPoint { Date = new DateTime(2017,12,13), Politics = 75,  Entertainment = 10 },
              new DataPoint { Date = new DateTime(2017,12,14), Politics = 65,  Entertainment = 0 }
          };
      }
  

  The chart below aggregates the data for the Entertainment and Politics series by month. The Entertainment series contains two empty points that are displayed differently - the series line does not break for “May 2017” despite the existing empty point, while “December 2016” is displayed as a break:

  

  The difference between the display of two intervals with empty points is that “December 2016” contains no data except an empty point, and “May 2017” contains several points in addition to an empty point.