AF SDK Reference

AFCalculation Class

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AFCalculation Class

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Last UpdatedNov 18, 2025
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AFCalculation Class

The static class AFCalculation provides mechanisms to evaluate expressions.

Inheritance Hierarchy

SystemObject
OSIsoft.AF.DataAFCalculation

Namespace: OSIsoft.AF.Data
Assembly: OSIsoft.AFSDK (in OSIsoft.AFSDK.dll) Version: 3.1.1.1182

Syntax

public static class AFCalculation

Public NotInheritable Class AFCalculation

You do not need to declare an instance of a static class in order to access its members.

public ref class AFCalculation abstract sealed

[<AbstractClassAttribute>]
[<SealedAttribute>]
type AFCalculation =  class end

The AFCalculation type exposes the following members.

Methods

	Name	Description
	CalculateAtIntervals	This method returns an AFValues collection that contains the result of evaluating the passed expression over the passed time range at a defined interval.
	CalculateAtRecordedValues	This method returns an AFValues collection that contains the result of evaluating the passed expression at each point in time over the passed time range where a recorded value exists for a member of the expression.
	CalculateAtTimes	This method returns an AFValues collection that contains the result of evaluating the passed expression over the passed points in time.
	CalculateSummaries	This method evaluates the specified expression over the passed time range. The passed time range is first divided into a number of summary intervals. The method then computes the specified summaries over each interval.
	ConvertExpressionTarget	Convert a Performance Equation (PE) Expression from one target to another.
	ConvertFilterTarget	Convert a Performance Equation Filter (PE) Expression used in a from one target to another.
	DetermineEvaluationServer	This method returns the server that the expression, with the specified target, will execute on.
	PercentTrue	This method evaluates the passed boolean expression over the passed time range. The passed time range is first divided into a number of calculation intervals. The method then computes the percentage of time the passed expression evaluates to true over each of the periods.

Remarks

Expression syntax follows PI Performance Equation syntax. Expression variables are references to Attributes or PI Points using relative syntax to the target, which is typically an AFDatabase, AFElement or a PIServer. Variables must be enclosed in single quotes. Calculations are limited to Attributes or PI Points which originate from a single PI Data Archive. Attributes which resolve to a static value (no data reference configured), are also acceptable.

Examples of valid target and expressions:

Target	Example Expression
null	'\\myPIServer\sinusoid'*2
null	'\\myAFServer\myDB\myElement\|myAttribute'*2
PIServer	'sinusoid'*2
AFDatabase	'myRootElement\myChildElement\|myAttribute'*2
AFElement	'myAttribute'*2
AFElement	'myAttribute\|myChildAttribute'*2
AFElement	'.\myChildElement\|myAttribute'*2
AFElement	'\\myPIServer\sinusoid'*2
AFEventFrame	'myAttribute'*2
AFAttribute	'.'*2
AFAttribute	'myChildAttribute'*2
AFAttribute	'..\|mySiblingAttribute'*2

Notes to Callers
This method, property, or class is not available in the legacy .NET 3.5 version of the SDK.

Examples

// This example demonstrates how to use the AFCalculation
// object to evaluate expressions for Attributes and PI Points.

// Get a Database
PISystems myPISystems = new PISystems();
PISystem myPISystem = myPISystems.DefaultPISystem;
AFDatabase myDB = myPISystem.Databases.DefaultDatabase;

// Create an Element
AFElement myElement = myDB.Elements.Add("MyElement");

// Create some attributes
AFAttribute myAttributeA = myElement.Attributes.Add("A");
myAttributeA.DataReferencePlugIn = AFDataReference.GetPIPointDataReference(myPISystem);
myAttributeA.ConfigString = @"\\%Server%\cdt158";

AFAttribute myAttributeB = myElement.Attributes.Add("B");
myAttributeB.Type = typeof(Single);
myAttributeB.SetValue(Math.PI, null);

// Calculate some interpolated values with AF Attributes
AFTimeRange timerange = new AFTimeRange("Y", "T", CultureInfo.CurrentCulture);
AFValues values = AFCalculation.CalculateAtIntervals(myElement, "'A' * 'B'", timerange, AFTimeSpan.Parse("1 hour"));
Console.WriteLine("Calculated Values at Intervals:");
foreach (AFValue value in values)
{
    Console.WriteLine("   '{0:0.000}' at '{1}'",
        value.Value, value.Timestamp);
}

// Calculate some values with PI Points
PIServer piserver = new PIServers().DefaultPIServer;
values = AFCalculation.CalculateAtRecordedValues(piserver, "'sinusoidu' + 'sinusoid'", timerange);
Console.WriteLine("Calculated Values at Recorded Values:");
foreach (AFValue value in values)
{
    Console.WriteLine("   '{0:0.000}' at '{1}'",
        value.Value, value.Timestamp);
}

// Calculate summaries, use both attributes and pi points
string expression = String.Format(CultureInfo.InvariantCulture, @"'A' * 'B' + '\\{0}\sinusoid'", piserver.Name);
IDictionary<AFSummaryTypes, AFValues> results = AFCalculation.CalculateSummaries(myElement, expression, timerange, AFTimeSpan.Parse("1 hour"),
    AFSummaryTypes.All | AFSummaryTypes.Average | AFSummaryTypes.Maximum | AFSummaryTypes.Minimum,
    AFCalculationBasis.TimeWeighted, AFSampleType.Interval, AFTimeSpan.Parse("5 minutes"), AFTimestampCalculation.Auto);

foreach (KeyValuePair<AFSummaryTypes, AFValues> result in results)
{
    Console.WriteLine("Summary Type {0} Results", result.Key);
    foreach (AFValue value in result.Value)
    {
        Console.WriteLine("   '{0:0.000}' at '{1}'",
            value.Value, value.Timestamp);
    }
}

' This example demonstrates how to use the AFCalculation
' object to evaluate expressions for Attributes and PI Points.

' Get the Database
Dim myPISystems As New PISystems
Dim myPISystem As PISystem = myPISystems.DefaultPISystem
Dim myDB As AFDatabase = myPISystem.Databases.DefaultDatabase

' Create An Element
Dim myElement As AFElement = myDB.Elements.Add("MyElement*")

' Create some Attributes
Dim myAttributeA As AFAttribute = myElement.Attributes.Add("A")
myAttributeA.DataReferencePlugIn = AFDataReference.GetPIPointDataReference(myPISystem)
myAttributeA.ConfigString = "\\%Server%\cdt158"

Dim myAttributeB As AFAttribute = myElement.Attributes.Add("B")
myAttributeB.Type = GetType(Single)
myAttributeB.SetValue(Math.PI, Nothing)

' Calculate some interpolated values with AF Attributes
Dim value As AFValue
Dim timerange As AFTimeRange = New AFTimeRange("Y", "T", CultureInfo.CurrentCulture)
Dim values As AFValues = AFCalculation.CalculateAtIntervals(myElement, "'A' * 'B'", timerange, AFTimeSpan.Parse("1 hour"))
Console.WriteLine("Calculated Values at Intervals:")
For Each value In values
    Console.WriteLine("   '{0:0.000}' at '{1}'", value.Value, value.Timestamp)
Next value

' Calculate some values with PI Points
Dim piserver As PIServer = New PIServers().DefaultPIServer
values = AFCalculation.CalculateAtRecordedValues(piserver, "'sinusoidu' + 'sinusoid'", timerange)
Console.WriteLine("Calculated Values at Recorded Values:")
For Each value In values
    Console.WriteLine("   '{0:0.000}' at '{1}'", value.Value, value.Timestamp)
Next value

' Calculate summaries, use both attributes and pi points
Dim expression As String = String.Format(CultureInfo.InvariantCulture, "'A' * 'B' + '\\{0}\sinusoid'", piserver.Name)
Dim results As IDictionary(Of AFSummaryTypes, AFValues)
results = AFCalculation.CalculateSummaries(myElement, expression, timerange, AFTimeSpan.Parse("1 hour"),
    AFSummaryTypes.All Or AFSummaryTypes.Average Or AFSummaryTypes.Maximum Or AFSummaryTypes.Minimum,
    AFCalculationBasis.TimeWeighted, AFSampleType.Interval, AFTimeSpan.Parse("5 minutes"), AFTimestampCalculation.Auto)

Dim result As KeyValuePair(Of AFSummaryTypes, AFValues)
For Each result In results

    Console.WriteLine("Summary Type {0} Results", result.Key)
    For Each value In result.Value
        Console.WriteLine("   '{0:0.000}' at '{1}'", value.Value, value.Timestamp)
    Next value
Next result

No code example is currently available or this language may not be supported.

AF SDK Reference