Ulrich,
as usual with such specific questions, it is a good idea to have the
package authors at least Cc (done now). In April I had already forwarded
your message privately to the plm authors with the following comment:
<comment>
I've quickly checked what is going on. If you do something like
foo <- "individual"
x <- plm(..., effect = foo)
plm:::desribe(x, "effect")
it doesn't work. describe() entirely relies on the call on x$call which
cannot know anymore what "foo" was (unless you would evaluate it again).
I would recommend to make the model object self-contained. Within plm()
you could do
result$args = list(model = model, effect = effect, ...)
etc. and then operate on that with describe(). That should be fully
backward compatible with your current approach.
</comment>
Best regards,
Z
On Mon, 3 Aug 2009, Ulrich Morawetz wrote:
Dear "plm"-Package insiders,
[I posted the following observation is April already but unfortunately I am not
aware of any answers.
With the hope that someone found an answer in the mean time, I ask again:]
I realized the following difficulty with the summary.plm function (demonstrated
with the example from the ?plm documentation).
library(plm)
data("Produc", package="Ecdat")
estimation_method<-"within"
estimation_effect<-"individual"
zz <- plm(log(gsp)~log(pcap)+log(pc)+log(emp)+unemp, data=Produc,
index=c("state","year")
, method=estimation_method
, effect=estimation_effect
)
summary(zz)
#Error: object of type 'symbol' is not subsettable
#But if I run
zz <- plm(log(gsp)~log(pcap)+log(pc)+log(emp)+unemp, data=Produc,
index=c("state","year")
, method="within"
, effect="individual"
)
summary(zz)
#the summary function works fine.
Is it wrong (or bad practice) to define the function's parameters as I did in
the upper example? If yes, how should it be done correctly such that the
summary function works?
I am running R version 2.9.1 wie plm version 1.1-4 on a Windows XP
workstation. I checked, and the same issue occurs under Linux (Ubuntu).
Thank you for your advice, Ulrich Morawetz
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