[R] plm function

Millo Giovanni Giovanni_Millo at Generali.com
Mon Mar 19 17:10:55 CET 2012

Dear Ieva,

plm(.., model="within") (which is the default for plm()) estimates a
within model on time-demeaned data, which is "equivalent" to using the
LSDV estimator. Therefore any time-constant dummy variable you add "by
hand" will be discarded because of perfect collinearity.

What kind of dummies are you trying to include? If they are
time-constant they will be incompatible with the within (FE) estimator,
but not with other uses of plm() like random effects ('model="random"')
or pooling ('model="pooling"').

A reproducible example, as requested by the posting guide, would have
clarified things.
Best wishes,

Giovanni Millo, PhD
Research Dept.,
Assicurazioni Generali SpA
Via Machiavelli 4,
34132 Trieste (Italy)
tel. +39 040 671184
fax  +39 040 671160

--------- original message ---------------------

Message: 15
Date: Wed, 14 Mar 2012 13:46:03 +0200
From: Ieva Sriubait? <ieva.sriubaite at gmail.com>
To: r-help at R-project.org
Subject: [R] plm function
<CAOCxseKEvj5uevHCNm-Or_E-yj=BacPB524TaZq-9Su+f+KjmA at mail.gmail.com>
Content-Type: text/plain

Dear Sir/ Madam,

I am writing about the panel data for my bachelor degree.
I would really appreciate if You could help dealing with R functions.
I am trying to estimate the panel data lm model with plm function. When
include 3dummy variables into the regression it dont appear in the
of the model, but when i estimate a simple lm model it appears.
Why is it so? What should i do to estimate the statistics for those

Thank You.

--------- end original message ---------------------

Ai sensi del D.Lgs. 196/2003 si precisa che le informazi...{{dropped:12}}

More information about the R-help mailing list