The NLMIXED Procedure
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Overview
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Getting Started
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Syntax
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Details
Modeling Assumptions and Notation Integral Approximations Built-in Log-Likelihood Functions Optimization Algorithms Finite-Difference Approximations of Derivatives Hessian Scaling Active Set Methods Line-Search Methods Restricting the Step Length Computational Problems Covariance Matrix Prediction Computational Resources Displayed Output ODS Table Names
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Examples
- References
| CONTRAST Statement |
- CONTRAST ’label’ expression <, expression> <options> ;
The CONTRAST statement enables you to conduct a statistical test that several expressions simultaneously equal zero. The expressions are typically contrasts—that is, differences whose expected values equal zero under the hypothesis of interest.
In the CONTRAST statement you must provide a quoted string to identify the contrast and then a list of valid SAS expressions separated by commas. Multiple CONTRAST statements are permitted, and results from all statements are listed in a common table. PROC NLMIXED constructs approximate 
tests for each statement using the delta method (Cox 1998) to approximate the variance-covariance matrix of the constituent expressions.
The following option is available in the CONTRAST statement:
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DF=
specifies the denominator degrees of freedom to be used in computing
values for the statistics. The default value corresponds to the DF= option in the PROC NLMIXED statement.