From marc_grt at yahoo.fr  Sun Jul  9 16:05:49 2017
From: marc_grt at yahoo.fr (Marc Girondot)
Date: Sun, 9 Jul 2017 16:05:49 +0200
Subject: [Rd] MASS:::dropterm.glm() and MASS:::addterm.glm() should use ...
 for extractAIC()
Message-ID: <89d0ae23-3560-8c1a-fcd9-4ead33a49496@yahoo.fr>

Here is a change required from MASS:::dropterm.glm() and 
MASS:::addterm.glm().

Thanks

Marc


The stepAIC() function from package MASS uses extractAIC() to get the 
AIC from a model.
Several methods exist:
extractAIC.glm() for example, some in MASS packages and some in stats 
package.

The parameters for extractAIC() are:
fit, scale, k = 2, ...

The ... are not used in most of the extractAIC.xxx() methods, from 
example in stats:::extractAIC.glm() or MASS:::extractAIC.loglm() but its 
presence could be necessary if extractAIC() is changed to use for 
example to use AICc rather than AIC.

Within stepAIC(), extractAIC() uses always the ... parameter. So all is 
ok for that.

However, stepAIC() uses dropterm() or addterm().

Within MASS:::dropterm.glm() and MASS:::addterm.glm(), extractAIC() is 
also used but without the ... parameter.

It prevents to use new version of extractAIC() that could use this 
parameter.

The solution is simple:
In MASS:::dropterm.glm(), line 60 and MASS:::addterm.glm(), line 84:
aic <- aic + (extractAIC(object, k = k)[2L] - aic[1L])
must be changed to
aic <- aic + (extractAIC(object, k = k, ...)[2L] - aic[1L])

Other dropterm.xxx() and addterm.xxx() do not suffer this problem.



[Rd] MASS:::dropterm.glm() and MASS:::addterm.glm() should use ... for extractAIC()
Marc Girondot