Abs (Tag-based PE function)

Abs function in PI Server's Performance Equations (PE) subsystem is used to return the absolute (non-negative) value of a number or the result of a numeric expression. This function is particularly helpful in scenarios where the direction of a value (positive or negative) is not relevant, such as when calculating differences or deviations between values.

Syntax

Abs(x)

Arguments

x

Must be an integer, real number, or tag that provides a numeric value.

Returns

The absolute (non-negative ) value of x.

Exceptions

If x is not an integer or real number, an error returns value is returned.

Example

Abs(1) // Returns: 1

Abs(-2.2) // Returns: 2.2

Abs('tag1') // Returns the absolute value of the current value of 'tag1'

Abs('tag1' - 'tag2

') // Returns the absolute value of the difference between 'tag1' and 'tag2'

Usage

The Abs function can be incorporated into PI Performance Equations to ensure values remain non-negative, a useful approach for monitoring metrics or conditions where only the magnitude of a change matters. For example, you could define a new Performance Equation tag in PI System Management Tools (SMT) to track the absolute difference between two tags, using an expression like:

Abs('tag1' - 'tag2')

This setup helps capture deviations or comparative metrics without considering positive or negative signs, making it ideal for applications that require non-directional data. For more information, see Performance equations (PE) syntax and functions reference.