systemfit (version 0.5-6)

sur: Seemingly Unrelated Regressions Estimation

Description

Fits a set of structural equations using Seemingly Unrelated Regressions. The resulting object is an array of fitting regression equations that contain information about the fitting process as well as the resulting parameter estimates, standard error estimates and covaraince matrix.

Usage

sur.systemfit( eqns, instruments, eqnlabels, data )

Arguments

eqns

a list of structural equations to be estimated; a regression constant is implied if not explicitly omitted.

instruments

one-sided model formula specifying instrumental variables. Instrument variables are not used in this case.

data

an optional data frame containing the variables in the model. By default the variables are taken from the environment from which sur is called.

eqnlabels

list of character vectors of names for the equation labels.

Value

• sur returns a list of objects of class sur, with the following components:
• n
  number of observations.
• p
  number of parameters.
• coefficients
  parameter estimates.
• V
  estimated covariance matrix of coefficients.
• s
  residual standard error.
• residuals
  vector of residuals.
• response
  vector of response values.
• X
  model matrix.
• response.name
  name of response variable, or expression evaluating to response.
• formula
  model formula.
• method
  estimation method for the object, in this case, "SUR".
• eqnlabel
  the equation label from the labels list for the equation.
• formula
  model formula.
• dfe
  error degrees of freedom.
• dfm
  model degrees of freedom.
• model.matrix
  model matrix for the ith equation
• model.frame
  model frame for the ith equation
• instruments
  list of instruments for the set of equations.
• response
  y
• predicted
  predicted values
• residuals
  residuals
• v
  v
• b
  parameter estimates
• n
  number of observations for the ith equation
• s
  estimation of sigma
• sse
  sum of squares
• mse
  mean squared error
• rmse
  square root of mse or root mean squared error
• se
  estimates standard errors of the parameter estimates.
• t
  t values for b
• p
  p values for b
• r2
  r2
• adjr2
  adjusted r-squared
• covb
  covb
• se.prediction
  standard error of the predicted values
• prediction.limits
  lower and upper 95 percent prediction limits
• confidence.limits
  lower and upper 95 percent confidence limits

References

Greene, W. H. (1993) Econometric Analysis, Second Edition, Macmillan. Kmenta, J. (1997) Elements of Econometrics, Second Edition, University of Michigan Publishing

See Also

ols,twostage,surand threestage

Examples

library( systemfit )

data( kmenta )
attach( kmenta )
demand <- q ~ p + d
supply <- q ~ p + f + a
inst <- ~ d + f + a
labels <- list( "demand", "supply" )
system <- list( demand, supply )

## perform SUR on each of the equations in the system
fitsur <- sur.systemfit( system, inst, labels, kmenta )
print( fitsur )
print( "covariance of residuals" )
print( varcov.systemfit( fitsur ) )