[R] To create a Panel and run a Pooled OLS

Spencer Graves spencer.graves at pdf.com
Mon Apr 21 04:50:35 CEST 2003

I just see a difference between what I wrote and what I use.  Have you 
tried the following:

	OLS <- lm(y~x1+x2, data=Panel)

spencer graves
If yes, could you replicate the error with a small data set that you
send with your help request?  It can make it easier for others to

Hope this helps. spencer graves

langensk at fas.harvard.edu wrote:
 > Dear all,
 > I have tried to merge two cross sections (crossA and crossB) as 
follows, both
 > crossA and crossB include the same variables, e.g., ID,y,x1,x2:
 > Panel <- merge(crossA,crossB,by="ID")
 > I have, thereafter, tried to run the following pooled OLS:
 > OLS <- lm(Panel$y~Panel$x1+Panel$x2)
 > and have received the following error message "Error in 
 > rownames, variables, varnames, extras, extranames,  : invalid 
variable type"
 > I would be very grateful for help. At the moment, I believe that I 
have tried
 > everything.
 > Thanks in advance,
 > Sophie
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