On Mon, 29 Mar 2010, serdal wrote:
hi,
i am writing my master thesis and i am dealing with 146474 observations
(panel data), i have just learned the R so i am a beginner!!
i am trying to use the "plm" package and i have a duplication problem;
i have written the following commands to read my data and create my model
dsn<-plm.data(ds, c("stno", "year")) ds=name of my data, stno=individual
effect, year=time effect
this command works just fine, i can even get the summary of "dsn" with
summary(dsn) which works fine also, however my problem starts when i define
my model and i cant find where do i make mistake!!
i try to create my model with the following command
dsn.plm <- plm(lnQ~lnC+lnL+lnM+lnE,data=ds,
random.method="walhus",effect="twoways",model="random")
and than i get this error message
duplicate couples (time-id)
Error in pdim.default(index[[1]], index[[2]]) :
The error is rather explicit, I think: There is at least one time
value (= year in your case) duplicated for at least one level of your id
variable (= stno) which is not supported.
An artificial example replicating this is:
dat <- data.frame(y = rnorm(7), x = rnorm(7), stno = rep(1:2, c(3, 4)),
year = c(2001:2003, 2001, 2001:2003))
pdat <- plm.data(dat, c("stno", "year"))
plm(y ~ x, data = pdat)
To find out which ID has duplicated times, you can do something like:
with(pdat, levels(stno)[tapply(year, stno,
function(x) any(table(x) > 1))])
hth,
Z
so my question is; is there anyone who knows how to overcome with this
error!
for now i dont know if i have to give more info and which info! but if you
think you can help me i am ready to send more info...
thanks for sparing your time!
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