data(GrunfeldGreene, package="systemfit")

library("plm")

GGPanel <- plm.data(GrunfeldGreene, c("firm", "year"))

form <- invest ~ value + capital



##Replicates the tables in Greene 2003 (5th Edition) Table 14.1

##OLS Estimation

greeneOLS <- systemfit(form, data=GGPanel)

round(coef(summary(greeneOLS)), digits=4)

round(sapply(greeneOLS$eq, function(x) {

	return(summary(x)$ssr/20)  }), digits=3)



##Pooled OLS

greeneOlsPooled <- systemfit(form, data = GGPanel, pooled = TRUE)

round(coef(summary(greeneOlsPooled$eq[[1]])), digits = 4)

sum(sapply(greeneOlsPooled$eq, function(x) { 

	return(summary(x)$ssr) }))/100



##SUR Estimation

greeneSur <- systemfit(form, method = "SUR", data = GGPanel,

	methodResidCov = "noDfCor")

round(coef(summary(greeneSur)), digits = 4)

round(greeneSur$residCov, digits = 3)

round(summary(greeneSur)$residCor, digits = 3)



#Pooled SUR Estimation

greeneSurPooled <- systemfit(form, method = "SUR",

	data = GGPanel, pooled = TRUE, methodResidCov = "noDfCor",

	residCovWeighted = TRUE)

round(coef(summary(greeneSurPooled$eq[[1]])), digits = 4)

round(greeneSurPooled$residCov, digits = 3)

round(cov(residuals(greeneSurPooled)), digits = 3)

round(summary(greeneSurPooled)$residCor, digits = 3)