*
* Example from page 182, section 6.6.
* Lin-Log model
*
open data table2-8.prn
data(format=prn,org=columns) 1 55
*
set logtotal = log(totalexp)
linreg foodexp
# constant logtotal
*
scatter(hlabel="Total Expenditures (Rs)",vlabel="Expenditure on Food (Rs)")
# totalexp foodexp
*
* Computing an elasticity. In the lin-log model (or almost any model other than
* log-log), the elasticity is different for different values of x. Here, we
* compute it at the sample mean of the log(totalexp) variable.
*
* If y=a + b log x, then dy/dx = dy/d(log X)*d(log X)/dx or b*(1/x). So
* (dy/dx)*(x/y)=b*(1/x)*x/y=b/y
*
compute xmean=%avg(logtotal)
disp "Estimated Elasticity at" xmean "is" %beta(2)/(%beta(1)+%beta(2)*xmean)