Dear R developers,
One function in my mkin package [1] returns an object that is originally
created by nlme(), but contains some additional information. Its class is
c("mmkin.nlme", "nlme", "lme").
Now I would like to use the anova() method for lme objects for comparing
such S3 objects. Unfortunately, anova.lme currently does not check for
inheritance, but checks the first element of the class attribute (as
obtained by data.class()) against a hardcoded list of classes in order to
decide if it will work or not.
Therefore, I created a bug report [2], containing a patch [3] for nlme that
makes anova.lme check for inheritance.
Encouraged by a kind comment by Elin Waring in the BTS, I have now revisited
my bug report, and discovered that the help page for data.class() claims
that its return value (the first element of the class attribute vector) is
"what is typically useful for method dispatching".
However, I think that this use case illustrates that it would be useful not
only to check for the primary class, but rather for class inheritance.
Do you agree that it is preferable for the S3 method to check for
inheritance instead of checking against a hardcoded list in this case?
Kind regards,
Johannes Ranke
[1] https://github.com/jranke/mkin/blob/master/R/nlme.mmkin.R
[2] https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17761
[3] https://bugs.r-project.org/bugzilla/attachment.cgi?id=2578