A relevant report, not just for VGAM but for maintainers of other
packages that define methods for functions that have both generic and
non-generic versions in other packages.
The problem is that VGAM "Depends" on stats4 but does not import from
it. So when VGAM is loaded, only the old version of summary() is
available. Importing the relevant functions from stats4 in VGAM should
fix the problem.
With the current R 2.14.1 this happens silently. With the latest
r-devel, the installation of VGAM produces a warning:
"Functions for exporting methods must have been made generic, explicitly
or implicitly; not true when loading 'VGAM' for 'AIC', 'coef', 'logLik',
'plot', 'summary', 'vcov' "
This implies (a bit obscurely) that the package has generic versions in
its dependencies, but has not imported them.
Maintainers of CRAN packages should check installation against the
development version. Warning messages like this suggest a problem with
the imports.
John
On 1/9/12 5:05 PM, mark.braving...@csiro.au wrote:
The symptom triggering this email is that an S4 summary method sometimes
refuses to be invoked, even when a package is explicitly loaded, if the first
load of the package is implicit. It may or may not be specific to 'summary'
methods and/or the 'VGAM' package. I've sent to R-devel because (i) it looks
like some kind of bug to me, but I'm not sure; (ii) it's not something I
personally need any help with; and (iii) it seems a bit specialized for R-help.
Here's the case notes. I have an object 'nf1' of S4 class 'vglm', created by calling 'vglm(...)'
from package 'VGAM' (you can create your own from the examples in VGAM). It's save()d into a file
"nf1.rda". If I start a new R session, call 'library( VGAM)', and then
'load("nf1.rda")', then 'summary(nf1)' works fine. But if instead I start a pretty basic
R session and load() the file *without* having explicitly called library( VGAM), the summary method
for 'vglm' doesn't get called whether or not I subsequently call library( VGAM). Transcript below.
I'm using R 2.13.2 on Windows XP, VGAM 0.8-4. The same thing happens with R
2.15 devel v57866.
bye
Mark
Mark Bravington
CSIRO CMIS
Marine Lab
Hobart
Australia
#############################
# Start a basic R session, and then:
search()
[1] ".GlobalEnv" "package:stats4" "package:splines" "package:stats"
"package:graphics"
[6] "package:grDevices" "package:utils" "package:datasets" "package:methods"
"Autoloads" "package:base"
print( load( "nf1.rda")) # which should implicitly load VGAM, but not attach it
[1] "nf1"
search()
# ...snipped. No explicit VGAM
loadedNamespaces()
# ...snipped. VGAM is there at the end.
nf1
Call:
vglm(formula = form, family = posbinomial, data = data, trace = TRUE)
Coefficients:
# ...snipped. The print() or show() or whatever method seems to get called OK
summary( nf1)
Length Class Mode
1 vglm S4
# Hmmm... default method is being called, that's wrong. Try explicitly
attaching 'VGAM':
library( VGAM)
Loading required package: splines
Loading required package: stats4
Attaching package: 'VGAM'
The following object(s) are masked from 'package:splines':
bs, ns
The following object(s) are masked from 'package:stats':
biplot, case.names, coefficients, df.residual, fitted, fitted.values,
formula, poly, residuals,
variable.names, weights
The following object(s) are masked from 'package:base':
identity, print, scale.default
summary( nf1)
Length Class Mode
1 vglm S4
# Hmmm... even though VGAM is on the search path etc, the wrong method is being
called
###############################
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