Concepts

Tasks

Settings

Using Logical Operators and Functions

Contents

Using a String in a Calculated Indicator

Using an Enumerated Attribute in a Calculated Indicator

Using a Boolean Attribute in a Calculated Indicator

Using an Array in a Calculated Indicator

Using a Date Attribute in a Calculated Indicator

A function is a series of VB.NET or C# statements that return a value. You can use functions to create a calculation for a calculated indicator or asset health calculation that includes logical operators such as IF, AND, OR, and so on. For example, you could do this if you want a calculation that includes an IF THEN statement.

Note: To create a calculation using a function, you should be familiar with VB.NET or C# scripting.

For example:

VB.NET

If A > B Then

return A

Else

return B

End if

C#

if (A > B)

{

return A;

]

else

[

return B;

}

Where A and B are the argument names.

A function returns a value by assigning a value to the function’s name in one or more statements of the procedure. The return data type of a function is always a Variant.

Calculation Inputs and Argument Names

In order for a function to work, the calculation input names defined for the indicator must match the arguments named in the function. Therefore, in this example you must also define calculation inputs named “A” and “B”. This is similar to entering a regular calculation expression.

When you define a calculation for an indicator without functions, the system processes the calculation by wrapping your expression in a function statement. For example, if your calculation is A / B, the system processes it as:

A / B

When you create a calculation by defining your own function, the system behaves similarly: in the first line of the statement the system inserts your calculation input names as arguments for the function. This means that you can leave the arguments for the function blank. However, for your own record-keeping, you will probably want to enter the argument names anyway.

Note: Your calculation input names must match the names of the arguments used in the function.

This topic explains in general terms how to add a function to your calculated indicator. For examples of how you can use functions, see the following topics:

•	Creating a Calculated Descriptive Indicator

•	Using a String in a Calculated Indicator

•	Using an Enumerated Attribute in a Calculated Indicator

•	Using a Boolean Attribute in a Calculated Indicator

•	Using an Array in a Calculated Indicator

•	Using a Date Attribute in a Calculated Indicator

For a list of logical operators and statements, see Functions and Logical Operators.

To Add a Function to a Calculated Indicator

1.	Open or create the indicator.

2.	Select the Calculation tab.

3.	Enter your function in the text box provided, using the syntax described at the beginning of this topic.

4.	Define the inputs for the calculation using the argument names defined in your function. You can create two types of calculation inputs: based on indicator readings or based on filters.

From the New list select either Indicator Input or Filter Input. The Calculation Input dialog appears. For detailed instructions, see the following topics:

•	Creating Calculation Inputs Based on Indicator Readings

•	Creating Calculation Inputs Based on Filters

5.	You can check the syntax (the order of the elements) of your calculation by clicking Check (Test). When you click this button, the system looks for errors in how you have typed the calculation.

6.	To use the test values on the inputs to complete a test calculation, click Calculate. You can use the result of this calculation to check that the function is giving the desired results.

7.	If necessary, you can change the Required Proximity of the calculation inputs.

Setting Name

Description

Required Proximity

This setting is only applicable when a calculation uses more than one indicator-reading-based calculation input. This rule does not apply to filter-based calculation inputs. This option sets the time proximity required for calculated, performance, or rule-based indicators. You can specify the length of time within which all readings must have been collected in order for APM to evaluate the rule or calculation. For example, you can specify that all indicator readings used in the rule or calculation must have been collected within one day of each other. If any of the indicators fall outside of the time period entered here, APM will not evaluate the rule or calculation. Note: Required proximity is only applicable if two or more calculation inputs are based on indicator readings and use the most recent reading in the input.

8.	Select the Frequency tab.

9.	In the Triggering mechanism section, select when and how the system triggers the calculation. If the calculation is to be triggered at a regular interval, define the scheduled interval for the indicator.

For detailed instructions, see Defining an Indicator’s Calculation Frequency.

10.	When you are finished, close the Indicator window.