Adds terms from a
REML fixed model into a Genstat regression (R.W. Payne).
|Controls printed output (
||Limit for expansion of terms; default 3|
||Whether to base ratios in accumulated summary on rms from model with smallest residual ss or smallest residual ms (
||One or two criteria to be printed with the models (
|TERMS = formula||Fixed terms to be added|
VRADD is one of several procedures designed to improve the process of determining the appropriate fixed terms to include in a
REML analysis. (The others are
VRTRY.) They do this by a generalized regression analysis, with a weight matrix based on variances estimated from the original
REML analysis (with the full fixed model). See
VRFIT for details.
Before fitting any terms, the
VRSETUP procedure must be called to make some checks, and initialize 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. However,
VRFIT will call
VRSETUP for you, if you have not done so already. The analysis will then be based on the most recent
REML analysis. To use an earlier analysis, you should call
VRSETUP yourself, setting its
SAVE option set to the save structure of the required
In principle the
VRFIT procedure should also be called before
VRADD is used. However,
VRADD will call
VRFIT with a null model (i.e. only the constant) if
VRFIT has not been used already. So you can start investigating the fixed model just by calling
VRSETUP will be called for you, automatically).
The terms to be fitted are specified by the
TERMS parameter, in a similar way to the
FIT directive. The
FACTORIAL option sets a limit (by default 3) on the number of factors and variates in each term. Terms containing more than that number are omitted.
grid is relevant only to the fitting of nonlinear models.) See
VRDISPLAY for more details.
DENOMINATOR option specifies how the residual is selected for the accumulated analysis of variance By default it is taken from the model with the smallest number of residual degrees of freedom. However, you can set
DENOMINATOR=ms to take it from the model with the smallest residual mean square.
SELECTION option specifies the statistics to be displayed in the summary of analysis as in the regression directives, except that again some irrelevant settings are omitted. See
VRDISPLAY for more details.
CAPTION 'VRADD 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 VRFIT [PRINT=estimates] Littersize VRADD [PRINT=estimates,accumulated] Sex*Dose