This function extracts the total number of 'observations' from a fitted panel model.
## S3 method for class 'panelmodel' nobs(object, ...) ## S3 method for class 'pgmm' nobs(object, ...)
The number of observations is usually the length of the residuals
nobs gives 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 estimated by
plm(..., model = "fd") where the model
frame does not yet contain the differences (see also
A single number, normally an integer.
# 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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