[R] Regressions with fixed-effect in R

[chen jia]

Hi there,

Maybe people who know both R and econometrics will be able to answer
my questions.

I want to run panel regressions in R with fixed-effect. I know two
ways to do it.
First, I can include factor(grouping_variable) in my regression equation.
Second, I plan to subtract group mean from my variables and run OLS
panel regression with function lm().

I plan to do it with the second way because the number of groups is
large, which incur computational problems inverting large
model-matrix.

I am interested in the R-squared and adjusted R-squared out of these
regressions.

Do I need to adjust my R-squared after I run OLS regressions with
demeaned variables?

Are there any functions that specifically deal with fixed-effects?

Thanks.

Best,
Jia