plm (version 0.2-2)

pdata.frame: Data frame for panel data

Description

a data.frame with further attributes useful for panel data

Usage

pdata.frame(x,id,time=NULL,name=NULL)
## S3 method for class 'pdata.frame':
summary(object,...)
## S3 method for class 'summary.pdata.frame':
print(x,...)

Arguments

x

a data.frame (a pdata.frame for the print and summary methods),

object

a pdata.frame object,

id

the individual index,

time

the time index,

name

the name of the pdata.frame (the name of x if NULL),

...

further arguments.

Value

• This function returns internally an object of class c("pdata.frame","data.frame"), which is a data.frame with three additional attributes :
• indexes
  a list containing the names of the individual (id) and time (time) index variables,
• pdim
  a list containing the dimension of the pdata.frame (see pdim),
• pvar
  a list of two logical vectors indicating whether each variable varies across individuals (id.var) and across time periods (time.var) (see pvar).

Details

id and time can be the names of the indexes contained in the data.frame if any. time may be omitted, in this case a new variable called "time" is added to the data.frame. For balanced panels, the argument id can be an integer. In this case, two new variables, "time" and "id" are added to the data.frame.

pdata.frame calls pdim to check for the individual and time dimensions of the panel and pvar to check for the individual and time variation of each variable.

All elements of a pdata.frame are of class pserie and have an attribute data which is the name of the pdata.frame. The print method is inherited from data.frame. A summary method is provided which add to the summary.data.frame method informations about the structure of the panel.

A as.data.frame method is also provided to coerce a pdata.frame to an ordinary data.frame. Finally, a pfix function is available to edit a pdata.frame. It mimics the behavior of fix (which is not a generic function). Only editing is possible, not modification.

See Also

pdim, pvar, pread.table.

Examples

library(Ecdat)

#There are 595 individuals

data(Wages)
pdata.frame(Wages,595)

# Gasoline contains two variables which are individual and time indexes
# The pdata.frame is called gas
data(Gasoline)
pdata.frame(Gasoline,"country","year",name="gas")
summary(gas)

# Hedonic is an unbalanced panel, townid is the individual index
data(Hedonic)
pdata.frame(Hedonic,"townid")