Forms a model-definition structure for a
REML analysis (R.W. Payne).
||Specifies the model-definition structure; no default (must be specified)|
||Description of the model (for output)|
||Fixed model terms; default
||How to treat the constant term (
||Limit on the number of factors or covariates in each fixed term; default 3|
||What adjustment to make to covariates before analysis (
||What changes to make to an existing model-definition structure (
||Specifies the initial model-definition structure, to modify when
||Factor defining the different experiments in a multi-experiment (meta-) analysis|
||Random model terms|
||Initial values for each component|
||How to constrain each variance component and the residual variance (
VFMODEL is one of a suite of procedures designed to simplify the assessment of alternative models for a
REML analysis. The first step is to form a model-definition structure for each candidate model, using the
VFSTRUCTURE procedures (these define the model settings controlled by the
VSTRUCTURE directives, respectively). The model-definition structures can then be used as input to procedures like
VARANDOM, which assesses possible random models.
VMODEL to specify each model, in turn, so that it can fit it using
REML. The relevant results from each fit are saved by the
VRACCUMULATE procedure, so that a decision about the recommended random model can be made once they have all been tried.
The model-definition structure is specified by the
MODELDEFINITION option, which must be set. The
DESCRIPTION option supplies a (brief, one-line) description to identify the model in the output.
Details of the model are specified by the
EXPERIMENTS options, and the
CONSTRAINTS parameters (which correspond to those options and parameters of the
You can set the
CHANGEITEMS option to modify an existing model-definition structure, instead of redefining it. Its settings then specify which aspects are to be changed. By default, the existing definition structure is supplied by
MODELSTRUCTURE (and the modified structure replaces the existing one). Alternatively, if you want to keep the existing structure, you can specify it separately, using the
Commands for: REML analysis of linear mixed models.
CAPTION 'VFMODEL example',\ 'Slate Hall Farm data (Guide to REML in Genstat, Section 1.8).';\ STYLE=meta,plain SPLOAD '%gendir%/data/slatehall.gsh' " define model for analysis as a Lattice square design " VFMODEL [MODELSTRUCTURE=Latticesq; DESCRIPTION='Lattice square analysis';\ FIXED=variety] replicates/(rows*columns) VMODEL Latticesq REML yield