Specifies the model for a REML analysis using a model-definition structure defined by VFMODEL (R.W. Payne).
Option
PRINT = string tokens |
Controls printed output (model, structure); default * i.e. none |
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Parameter
MODELSTRUCTURE = pointer |
Model-definition structure |
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Description
VMODEL 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 VFMODEL and VFSTRUCTURE procedures (these define the model settings controlled by the VCOMPONENTS and VSTRUCTURE directives, respectively). The model-definition structures can then be used as input to procedures like VARANDOM, which assesses possible random models. VARANDOM uses 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.
Printed output is controlled by the PRINT option, with settings:
model |
uses the VSTATUS directive to print details of the model that has been specified, and |
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structure |
shows the contents of the model-definition structure (to help check for any errors in the definition). |
The model-definition structure is supplied by the MODELDEFINITION parameter.
Option: PRINT.
Parameter: MODELSTRUCTURE.
See also
Directives: REML, VCOMPONENTS, VSTRUCTURE.
Procedures: VARANDOM, VFMODEL, VFSTRUCTURE.
Commands for: REML analysis of linear mixed models.
Example
CAPTION 'VMODEL example',\
'Slate Hall Farm data (Guide to REML in Genstat, Section 1.8).';\
STYLE=meta,plain
SPLOAD '%gendir%/data/slatehall.gsh'
" analyse as a Lattice square design "
VFMODEL [MODELSTRUCTURE=Latticesq; DESCRIPTION='Lattice square';\
FIXED=variety] replicates/(rows*columns)
VMODEL Latticesq
REML yield
" analyse with an Ar1 (x) Ar1 model "
VFMODEL [MODELSTRUCTURE=AR1xAR1; DESCRIPTION='Ar1 (x) AR1';\
FIXED=variety] fieldrow.fieldcolumn
VFSTRUCTURE [MODELSTRUCTURE=AR1xAR1; TERMS=fieldrow.fieldcolumn]\
2('AR'); ORDER=1; FACTOR=fieldrow,fieldcolumn
VMODEL AR1xAR1
REML [PRINT=model,components,wald] yield