pdim: Check for the Dimensions of the Panel
In plm: Linear Models for Panel Data

Description Usage Arguments Details Value Note Author(s) See Also Examples

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

pdim(x, ...)

## Default S3 method:
pdim(x, y, ...)

## S3 method for class 'data.frame'
pdim(x, index = NULL, ...)

## S3 method for class 'pdata.frame'
pdim(x, ...)

## S3 method for class 'pseries'
pdim(x, ...)

## S3 method for class 'panelmodel'
pdim(x, ...)

## S3 method for class 'pgmm'
pdim(x, ...)

## S3 method for class 'pdim'
print(x, ...)

`x`	a `data.frame`, a `pdata.frame`, a `pseries`, a `panelmodel`, or a `pgmm` object,
`...`	further arguments.
`y`	a vector,
`index`	see `pdata.frame()`,

pdim is called by the estimation functions and can be also used stand-alone.

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 (of type integer): `Ti` gives the number of observations for each individual 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.

Calling pdim on an estimated panelmodel object and on the corresponding (p)data.frame used for this estimation does not necessarily yield the same result. When called on an estimated panelmodel, the number of observations (individual, time) actually used for model estimation are taken into account. When called on a (p)data.frame, the rows in the (p)data.frame are considered, disregarding any NA values in the dependent or independent variable(s) which would be dropped during model estimation.

Yves Croissant

is.pbalanced() to just determine balancedness of data (slightly faster than pdim),
punbalancedness() for measures of unbalancedness,
nobs(), pdata.frame(),
pvar() to check for each variable if it varies cross-sectionally and over time.

# 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)