R/S compatibility in passing a formula

Peter Dalgaard BSA p.dalgaard@biostat.ku.dk
11 Apr 1999 02:16:31 +0200

Douglas Bates <bates@stat.wisc.edu> writes:

> In S3 if you are passing an evaluated formula to another function that
> will store it and use it in printing (such as a model-fitting function), you
> usually want to unclass the formula.  Otherwise, the formula that gets
> stored looks very ugly when printed.  A trick to do the unclassing is to pass
>  form = c( myFormula )
> In R this has the effect of making form a list rather than a call.  It
> seems that passing
>  form = as.vector( myFormula )
> will work in both dialects.  Anyone else have experience with this?


(a) R does not print the class on a formula (because print.formula
unclasses it)
(b) as.vector does not unclass in R but does in S3. Try

So the result of as.vector *looks* alike, but isn't. Smells like

Whatever is wrong with using unclass() for unclassing anyway??

   O__  ---- Peter Dalgaard             Blegdamsvej 3  
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