On Tue, 2009-02-03 at 13:30 -0800, Nathaniel Smith wrote:
> why does EnvironmentSexp_ass_subscript (==
> rpy2.rinterface.SexpEnvironment.__setitem__) copy the value it is
> storing?
>
> PROTECT(sexp_copy = Rf_duplicate(sexp));
> Rf_defineVar(sym, sexp_copy, rho_R);
That's from the early development days, when I was getting very frequent
segfaults. That was to be on the safe side since R itself is often doing
a lot of copies; a second look at that (and try to minimize the number
of copies) is on the ever growing to-do list...
> I noticed this because I was trying to get dim<- to work on an
> SexpVector -- r["dim<-"](mysexp, newdim) doesn't work (more about that
> in a follow-up note), and the workaround would be something like
> globalEnv["mysexp"] = mysexp
> globalEnv["newdim"] = newdim
> r("dim(mysexp) <- newdim")
> But that is thwarted by the above call to Rf_duplicate. I guess I
> could do the above and then
> mysexp = globalEnv["mysexp"]
> but that seems silly.
I am a little confused regarding whether you would like to do things at
the robjects or the rinterface level. Either way, things seem to be
working on my end.
# rinterface
import rpy2.rinterface as ri
ri.initr()
x = ri.FloatSexpVector([1,2,3,4])
x = ri.globalEnv.get("dim<-")(x, ri.IntSexpVector([2, 2]))
ri.globalEnv.get("print")(x)
# with robjects
import rpy2.robjects as ro
x = ro.FloatVector([1,2,3,4])
x = ro.r["dim<-"](x, ro.IntVector([2, 2]))
L.
> -- Nathaniel
>
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