data( germanFarms )
# output quantity:
germanFarms$qOutput <- germanFarms$vOutput / germanFarms$pOutput
# quantity of variable inputs
germanFarms$qVarInput <- germanFarms$vVarInput / germanFarms$pVarInput
# a time trend to account for technical progress:
germanFarms$time <- c(1:20)
# estimate a quadratic production function
estResult <- quadFuncEst( "qOutput", c( "qLabor", "land", "qVarInput", "time" ),
germanFarms )
quadFuncCalc( c( "qLabor", "land", "qVarInput", "time" ), germanFarms,
coef( estResult ) )
#equal to estResult$fitted
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