Sets up Genstat regression to assess terms from a REML fixed model (R.W. Payne).
Option
SAVE = REML save structure |
Specifies the analysis whose fixed terms are to be tested; by default this will be the most recent REML |
Description
VRSETUP sets up Genstat regression to enable procedures VRFIT, VRADD, VRDROP, VRSWITCH, VRTRY, VRDISPLAY and VRKEEP, to be used to assess the terms in a REML fixed model. See VRFIT for details.
By default, VRSETUP takes the most recent REML analysis. However, you can take an earlier analysis, by using the SAVE option of VRTSETUP to specify its save structure (saved using the SAVE parameter of the earlier REML command).
VRSETUP first makes some checks to ensure that the REML analysis was successful, and that it is feasible to use regression. This cannot be used if the REML analysis did not estimate the constant term, or if it included any units with missing explanatory units (i.e. if the original REML command had option CONSTANT = omit, or option MVINCLUDE = explanatory). VRSETUP then obtains the unit-by-unit variance-covariance matrix (using the UVCOVARIANCE option of VKEEP), and inverts it to provide the weight matrix for the regression. It initializes the regression by specifying a MODEL command with the necessary weight matrix, and a TERMS command with the full fixed model. It also uses the WORKSPACE directive to set up a Genstat workspace structure to store control information and results for use by the other procedures.
Option: SAVE.
Parameters: none.
Action with RESTRICT
Any restriction applied to vectors used in the REML analysis will apply also to the results from VRFIT etc.
See also
Directives: FIT, REML.
Procedures: VRADD, VRDROP, VRFIT, VRDISPLAY,VRSWITCH, VRKEEP, VRTRY.
Commands for: REML analysis of linear mixed models.
Example
CAPTION 'VRSETUP example',\
'Example 5.3.6 from The Guide to Genstat, Part 2 Statistics';\
STYLE=meta,plain
FACTOR [NVALUES=322; LEVELS=27] Dam
& [NVALUES=322; LEVELS=18] Pup
FACTOR [NVALUES=322; LEVELS=2; LABELS=!T('M','F')] Sex
FACTOR [NVALUES=322; LEVELS=3; LABELS=!T('C','Low','High')] Dose
VARIATE [NVALUES=322] Littersize,Weight
OPEN '%GENDIR%/Examples/GuidePart2/Rats.dat'; CHANNEL=chan
READ [CHANNEL=chan] Dose,Sex,Littersize,Dam,Pup,Weight; \
FREPRESENTATION=2(labels),4(levels)
CLOSE chan
VCOMPONENTS [FIXED=Littersize+Dose*Sex] RANDOM=Dam/Pup
REML [PRINT=model,components,wald] Weight; SAVE=wsave
REML [PRINT=model,components,wald] LOG10(Weight)
VRSETUP [SAVE=wsave]
VRFIT [PRINT=estimates,accumulated] Littersize+Sex*Dose