data( "Kmenta" )
demand <- consump ~ price + income
supply <- consump ~ price + farmPrice + trend
labels <- list( "demand", "supply" )
system <- list( demand, supply )
## perform OLS on each of the equations in the system
fitols <- systemfit( "OLS", system, labels, data = Kmenta )
## variance covariance matrix of all coefficients
vcov( fitols )
## variance covariance matrix of the coefficients in the first equation
vcov( fitols$eq[[1]] )
## variance covariance matrix of the coefficients in the second equation
vcov( fitols$eq[[2]] )
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