Adds terms from a REML fixed model into a Genstat regression (R.W. Payne).
Options
PRINT = string tokens |
Controls printed output (model, deviance, summary, estimates, correlations, fittedvalues, accumulated); default mode, summ, esti, accu |
DENOMINATOR = string token |
Whether to base ratios in accumulated summary on rms from model with smallest residual ss or smallest residual ms (ss, ms); default ss |
SELECTION = string tokens |
One or two criteria to be printed with the models (%variance, %ss, adjustedr2, r2, dispersion, aic, sic, bic); default %var, aic, sic |
No parameters
Description
VRDISPLAY displays output from models fitted by procedures VRFIT, VRADD, VRDROP, VRSWITCH and VRTRY, which are designed to improve the process of determining the appropriate fixed terms to include in a REML analysis. 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). The models are thus assessed against identical estimates of the random variation (as in an analysis of variance), allowing statistics such as the Akaike information criterion to be used to assess which model may be best. Conversely, if you try to assess the fixed model by changing the fixed model in a sequence of VCOMPONENTS commands, the fixed terms that are not fitted will be included in the random variation. This will then vary from fit to fit, making it difficult to reach a clear and consistent conclusion. See VRFIT for more details.
The PRINT option controls printed output as in the regression directives, except that some irrelevant settings are omitted. The available settings are as follows.
model description of the currently fitted model, including response and explanatory variates,
deviance abbreviated summary analysis of variance,
summary summary analysis of variance,
estimates estimates of the parameters in the model,
correlations correlation matrix of the parameter estimates,
fittedvalues table with unit labels, values of response variate, fitted values, standardized residuals and leverages, and
accumulated analysis of variance table showing the various changes that have been made to the model.
The 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.
The 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. The available settings are as follows.
%variance percentage variance accounted for by the currently fitted model,
%ss percentage sum of squares accounted for,
adjustedr2 proportion of variance accounted for (i.e. %variance / 100),
r2 proportion of the sum of squares accounted for (i.e. %ss / 100),
dispersion dispersion parameter (which is equal to the residual mean square for an ordinary regression like this),
aic Akaike information criterion, and
sic or bic Schwarz (Bayesian) information criterion.
Options: PRINT, DENOMINATOR, SELECTION.
Parameters: none.
See also
Directives: RDISPLAY, REML.
Procedures: VRADD, VRDROP, VRFIT, VRKEEP, VRSETUP, VRSWITCH, VRTRY.
Commands for: REML analysis of linear mixed models.
Example
CAPTION 'VRDISPLAY 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=accumulated] Littersize+Sex*Dose
VRDISPLAY [PRINT=estimates]