plm (version 1.5-12)

pdim: Check for the Dimensions of the Panel

Description

This function checks the number of individuals and time observations in the panel and whether it is balanced or not.

Usage

pdim(x,...)
"pdim"(x, index = NULL, ...)
"pdim"(x, ...)
"pdim"(x, ...)

Arguments

x

a data.frame, a pdata.frame or a panelmodel object,

index

see pdata.frame,

...

further arguments.

Value

An object of class pdim containing the following elements:

nT

a list containing n, the number of individuals, T, the number of time observations, N the total number of observations,

Tint

a list containing two vectors : Ti gives the number of observations for each individuals and nt gives the number of individuals observed for each period,

balanced

a logical value : TRUE for a balanced panel, FALSE for an unbalanced panel,

panel.names

a list of character vectors : id.names contains the names of each individual and time.names contains the names of each period.

Details

pdim is called by the estimation functions.

See Also

nobs, pdata.frame

Examples

# There are 595 individuals

data("Wages", package = "plm")
pdim(Wages, 595)

# Gasoline contains two variables which are individual and time indexes
# and are the first two variables
data("Gasoline", package="plm")
pdim(Gasoline)

# Hedonic is an unbalanced panel, townid is the individual index
data("Hedonic", package = "plm")
pdim(Hedonic, "townid")

# An example of the panelmodel method
data("Produc", package = "plm")
z <- plm(log(gsp)~log(pcap)+log(pc)+log(emp)+unemp,data=Produc,
         model="random", subset = gsp > 5000)
pdim(z)