stepwise {gRc}R Documentation

Stepwise model selection in RCOX models

Description

These allow for stepwise model selection in RCOX models by. Model expansion (i.e. forward selection) is obtained by adding edge colour classes and by splitting edge/vertex colour classes. Model reduction (i.e. backward selection) is obtained by dropping edge colour classes and by joining edge/vertex colour classes.

Usage

stepadd1  (object, criterion = "aic", steps = 1000, k = 2, alpha = 0.05, details=1, trace=0)
stepdrop1 (object, criterion = "aic", steps = 1000, k = 2, alpha = 0.05, stat = "wald", details=1, trace=0) 
stepjoin1 (object, scope, type = "ecc", criterion = "aic", steps = 1000, k = 2, alpha = 0.05, stat = "wald",   details = 1, trace=0) 
stepsplit1(object, type = "ecc", criterion = "aic", steps = 1000, k = 2, alpha = 0.05, stat = "wald",   details = 1, trace=0) 

Arguments

object An RCOX model, an object of class RCOX
scope A set (list) of items (edge colour classes or vertex colour classes) to be considered. If missing, then all items are considered.
criterion Either "aic" (the default), "bic" or "test" (for significance test)
type Either "ecc" for edge colour classes or "vcc" for vertex colour classes.
k The multiple of the number of degrees of freedom used for the penalty when criterion is "aic". Ignored when criterion is "bic" or "test". Only k = 2 gives the genuine AIC.
steps The maximum number of steps to be considered. The default is 1000 (essentially as many as required). It is typically used to stop the process early
stat Either "wald" for a Wald statistic or "dev" for a deviance statistic.
alpha Critical value if 'criterion' is "test". If criterion is "aic" or "bic", the critical value is 0.
details Control the amount of output created.
trace For debugging purposes

Value

Either NULL or a new RCOX model.

Note

Note that the keyword 'stat' is not available for stepadd1 and stepsplit1 because these functions expand the current model and hence the Wald statistic is not available.

Author(s)

Søren Højsgaard, sorenh@agrsci.dk

See Also

split1 join1 add1.rcox drop1.rcox comparecc


[Package gRc version 0.2.2 Index]