Choose a trend function for a Gaussian process surrogate

Specification

Alias: none

Argument(s): none

Default: reduced_quadratic

Required/Optional	Description of Group	Dakota Keyword	Dakota Keyword Description
Required (Choose One)	Group 1	constant	Constant trend function
		linear	Use a linear polynomial or trend function
		reduced_quadratic	Quadratic polynomials - main effects only
		quadratic	Use a quadratic polynomial or trend function

Description

The only trend functions that are currently supported are polynomials.

The trend function is selected using the trend keyword, with options constant, linear, or reduced_quadratic. The reduced_quadratic trend function includes the main effects, but not mixed/interaction terms. The Surfpack GP (See surfpack) has the additional option of (a full) quadratic.