Create an expression analysis

In PI System Explorer, you can create a unique expression analysis for an individual element. In the analysis, you can create an expression for each calculation. To record the value that an expression calculates, map the output to an attribute. You can create new attributes as you configure an analysis.

1. In the navigator, click Elements.

2. In the Elements browser, select the element where you want to create the analysis.

3. In the viewer, click the Analyses tab.

   The tab lists any analyses already defined for the element.

4. Create a new analysis for the element:

   • If no analyses exist, click Create a new analysis to create the first one.

   • Otherwise, click New Analysis to create a new one.

5. Enter information to identify the analysis:

   • Name

     The name that uniquely identifies this analysis.

   • Description

     Optional text that describes the analysis.

   • Categories

     Optional category that you can assign to the analysis. Click the list and select the check box next to categories you want to assign or click New to create a new category.

   • Analysis Type

     Click Expression.

6. Specify one or more expressions for the analysis.

   Enter each expression in a row. An expression specifies inputs and calculations. See Understand expression analyses.

7. Map at least one expression to an output attribute:

   1. In the Output Attribute column for the expression, click Map.

   2. Specify the attribute.

   To ...	Do this ...
   Map the output to an existing attribute	Click the name of the attribute. Select an attribute with a PI point data reference to store the history of the calculation. For best performance when you do not require history, use an attribute with an analysis data reference.
   Map the output to a new attribute	Click New Attribute to open the Attribute Properties window. Indicate whether the attribute should save the history of the output: Click Yes to create an attribute with a PI point data reference. This attribute saves the history of the output. Click No to create an attribute with an analysis data reference. This attribute calculates a new value when requested. Configure the attribute: Name Name of created attribute. Description Optional text that describes the attribute. Data Server For attributes that save output history, the Data Archive server that stores the PI point data reference. By default, this is set to %Server%, which sets to the default Data Archive server. Value Type The data type the attribute stores. After creating the attribute, you can refine its definition from the Attributes tab. Click OK to create the attribute.

8. Optional. Click Evaluate to verify the output values at both Value at Last Trigger and Value at Evaluation times.

   Specify scheduling for the analysis. See Analysis scheduling.

9. Optional. To verify the analysis, review the results produced with historical data:

   1. In the analysis list, right-click the analysis and then click Preview Results.

   2. Enter a start time and end time not later than the current time, and click Generate Results to see a list of results.

10. To apply changes and save your work locally, click on the toolbar.

    This does not run the analysis.

11. Click Check In on the toolbar.

PI System Explorer saves and checks in your analysis, and then starts running the analysis.