This function extracts the total number of 'observations' from a fitted panel model.
The number of observations is usually the length of the residuals vector. Thus,
the number of observations actually used by the estimation procedure. It is not necessarily the number
of observations of the model frame (number of rows in the model frame), because sometimes the model frame
is further reduced by the estimation procedure. This is e.g. the case for first–difference models
plm(..., model = "fd") where the model frame does not yet contain the differences (see
A single number, normally an integer.
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# estimate a panelmodel data("Produc", package = "plm") z <- plm(log(gsp)~log(pcap)+log(pc)+log(emp)+unemp,data=Produc, model="random", subset = gsp > 5000) nobs(z) # total observations used in estimation pdim(z)$nT$N # same information pdim(z) # more information about the dimensions (no. of individuals and time periods) # illustrate difference between nobs and pdim for first-difference model data("Grunfeld", package = "plm") fdmod <- plm(inv ~ value + capital, data = Grunfeld, model = "fd") nobs(fdmod) # 190 pdim(fdmod)$nT$N # 200
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