Nothing
frontier <- function(
yName, xNames = NULL, zNames = NULL, data,
zIntercept = FALSE,
... ) {
# check names of variables
checkNames( c( yName, xNames ), names( data ) )
if( !is.null( zNames ) ) {
if( !is.na( zNames[1] ) ) {
checkNames( c( zNames ), names( data ) )
}
}
if( any( c( "id", "t" ) %in% c( yName, xNames, zNames ) ) ) {
stop( "variables in arguments 'yName', 'xNames', and 'zNames'",
" must not have names 'id' or 't'" )
}
# zIntercept (mu)
if( !is.logical( zIntercept ) ) {
stop( "argument 'zIntercept' must be logical" )
}
if( zIntercept && is.null( zNames ) ) {
warning( "argument 'zIntercept' is ignored in",
" Efficiency Components Frontiers (ECF)" )
}
# formula for the SFA
sfaFormula <- paste( yName, "~",
paste( c( "1", xNames ), collapse = " + " ) )
# formula for efficiency effects
if( is.null( zNames ) ) {
sfaFormula <- as.formula( sfaFormula )
} else {
if( is.na( zNames[1] ) ) {
if( zIntercept ) {
effFormula <- "1"
} else {
effFormula <- "- 1"
}
} else {
if( zIntercept ) {
effFormula <- paste( zNames, collapse = " + " )
} else {
effFormula <- paste( paste( zNames, collapse = " + " ), "- 1" )
}
}
sfaFormula <- as.formula( paste( sfaFormula, "|", effFormula ) )
}
returnObj <- sfa(
formula = sfaFormula,
data = data,
... )
returnObj$zIntercept <- zIntercept
returnObj$call <- match.call()
return( returnObj )
}
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