index.plm {plm} | R Documentation |
This function extracts the information about the structure of the individual and time dimensions of panel data.
## S3 method for class 'pindex' index(x, which = NULL, ...) ## S3 method for class 'pdata.frame' index(x, which = NULL, ...) ## S3 method for class 'pseries' index(x, which = NULL, ...) ## S3 method for class 'panelmodel' index(x, which = NULL, ...)
x |
an object of class |
which |
the index(es) to be extracted (see details), |
... |
further arguments. |
panel data are stored in a "pdata.frame"
which has an
"index"
attribute. Fitted models in "plm"
has a
"model"
element which is also a "pdata.frame"
and
therefore also have an "index"
attribute. Finally, each series
in a "pdata.frame"
is of class "pseries"
, which also
have this "index"
attribute. "index"
methods are
available for all these objects. The argument "which"
indicates
which index should be extracted. If NULL
, both indexes are
extracted, but "which"
can also be a vector of lenght 1 or 2
containing either characters (the names of the individual and of the
time periods or "id"
and "time"
) or integers (1 for the
individual index and 2 for the time index.)
a vector or a "data.frame"
containing either one or both
indexes.
Yves Croissant
data("Grunfeld", package = "plm") Gr <- pdata.frame(Grunfeld, index = c("firm", "year")) m <- plm(inv ~ value + capital, data = Gr) index(Gr, "firm") index(Gr, "time") index(Gr$inv, c(2, 1)) index(m, "id")