ChartCalculatedField Class

A calculated field.

Namespace: DevExpress.XtraCharts

Assembly: DevExpress.XtraCharts.v20.2.dll

NuGet Packages: DevExpress.Charts, DevExpress.WindowsDesktop.Charts

Declaration

C#

public class ChartCalculatedField :
    ChartElementNamed,
    IChartCalculatedField,
    ICalculatedField

VB.NET

Public Class ChartCalculatedField
    Inherits ChartElementNamed
    Implements IChartCalculatedField,
               ICalculatedField

Related API Members

The following members return ChartCalculatedField objects:

• ChartCalculatedFieldCollection.Item[Int32]
• ChartCalculatedFieldCollection.Item[String]

Remarks

Calculated fields allow you to evaluate values based on an expression and use them as a data source for series arguments,values, tooltips, crosshair label, and so on.

To add a calculated field to a Chart Control, add a ChartCalculatedField object to the ChartControl.CalculatedFields collection and specify the following parameters:

• Expression - An expression is a string that, when parsed and processed, evaluates a value. Expressions can consist of column/field names in brackets, constants, operators, and functions. Refer to Criteria Language Syntax for information on expression syntax.

• FieldType - Specifies the type of resulting values. The ChartCalculatedFieldType enumeration lists supported types.

• Name (inherited from ChartElementNamed) - The calculated field’s unique name. Avoid dots in names because the Chart uses dots to access data source members. Use the name to specify series data members (for example, SeriesBase.ArgumentDataMember, SeriesBase.ValueDataMembers, SeriesBase.ToolTipHintDataMember, or SeriesBase.ColorDataMember). You can also use calculated field names to configure text patterns.

Optional parameters:

• DataSource - Allows you to specify a custom data source to evaluate the specified expression. The calculated field and series must use the same data source. Series can obtain data from the chart’s data source or can be bound to a separate data source (see the Series.DataSource property). If the calculated field’s DataSource property is not specified, the field uses the corresponding series’s data source.

• DataMember - Allows you to specify the name of the sub-list or table if the data source contains more than one distinct list of data items.

• DisplayName - The calculated field’s display name that appears in the Chart Designer‘s Chart Data tab. If DisplayName is not specified, the Name property value is used instead.

Example

The following example shows how to create a calculated field and then use this field as a data source for a series. The field’s values are calculated by the following expression: [Time.Seconds] * [Velocity].

C#

using DevExpress.XtraCharts;
using System;
using System.Collections.Generic;
using System.Windows.Forms;

namespace CalculatedFieldExample {
    public partial class Form1 : Form {
        //...
        private void Form1_Load(object sender, EventArgs e) {
            chartControl1.DataSource = GetDataPoints();

            ChartCalculatedField calcField = new ChartCalculatedField();
            calcField.Expression = "[Time.Seconds] * [Velocity]";
            calcField.FieldType = ChartCalculatedFieldType.Double;
            calcField.Name = "Displacement";
            chartControl1.CalculatedFields.Add(calcField);

            Series series = new Series("series", ViewType.Line);
            series.ArgumentDataMember = "Time";
            series.ValueDataMembers.AddRange("Displacement");
            chartControl1.Series.Add(series);
            XYDiagram diagram = chartControl1.Diagram as XYDiagram;
            diagram.AxisX.TimeSpanScaleOptions.MeasureUnit = TimeSpanMeasureUnit.Second;
            diagram.AxisY.WholeRange.AlwaysShowZeroLevel = false;
        }
        public List<DataPoint> GetDataPoints() {
            List<DataPoint> dataPoints = new List<DataPoint>() {
                new DataPoint (new TimeSpan(0, 0, 0), 10),
                new DataPoint (new TimeSpan(0, 0, 1), 11.46),
                new DataPoint (new TimeSpan(0, 0, 2), 11.90),
                //...
                // Other data points here.
                // ...
                new DataPoint (new TimeSpan(0, 0, 12), 15.756)
            };
            return dataPoints;
        }
    }
    public class DataPoint {
        public TimeSpan Time { get; set; }
        public double Velocity { get; set; }
        public DataPoint(TimeSpan time, double velocity) {
            this.Time = time;
            this.Velocity = velocity;
        }
    }
}

VB.NET

Imports DevExpress.XtraCharts
Imports System
Imports System.Collections.Generic
Imports System.Windows.Forms

Namespace CalculatedFieldExample
    Public Partial Class Form1
        Inherits Form
        '...
        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs)
            chartControl1.DataSource = GetDataPoints()

            Dim calcField As ChartCalculatedField = New ChartCalculatedField()
            calcField.Expression = "[Time.Seconds] * [Velocity]"
            calcField.FieldType = ChartCalculatedFieldType.[Double]
            calcField.Name = "Displacement"
            chartControl1.CalculatedFields.Add(calcField)

            Dim series As Series = New Series("series", ViewType.Line)
            series.ArgumentDataMember = "Time"
            series.ValueDataMembers.AddRange("Displacement")
            chartControl1.Series.Add(series)
            Dim diagram As XYDiagram = TryCast(chartControl1.Diagram, XYDiagram)
            diagram.AxisX.TimeSpanScaleOptions.MeasureUnit = TimeSpanMeasureUnit.Second
            diagram.AxisY.WholeRange.AlwaysShowZeroLevel = False
        End Sub
        Public Function GetDataPoints() As List(Of DataPoint)
            Dim dataPoints As List(Of DataPoint) = New List(Of DataPoint)() From {
                New DataPoint(New TimeSpan(0, 0, 0), 10),
                New DataPoint(New TimeSpan(0, 0, 1), 11.46),
                New DataPoint(New TimeSpan(0, 0, 2), 11.90),
                '...
                ' Other data points here.
                '...
                New DataPoint(New TimeSpan(0, 0, 12), 15.756)
            }
            Return dataPoints
        End Function
    End Class
    Public Class DataPoint
        Public Property Time As TimeSpan
        Public Property Velocity As Double
        Public Sub New(ByVal time As TimeSpan, ByVal velocity As Double)
            Me.Time = time
            Me.Velocity = velocity
        End Sub
    End Class
End Namespace

Inheritance

Object

ChartElement

ChartElementNamed

ChartCalculatedField