st: computing elasticities after using lpoly

[Arka Roy Chaudhuri <gabuisi@gmail.com>]

Hi,

I am using Stata 11 on a Windows 7 machine. I am using lpoly to
estimate nonparametric regressions of the form:

log(y)=f(log(x)) + u

where y= per capita expenditure on food
x= total per capita expenditure

Using lpoly, I can get a graph of per capita expenditure on food
against total per capita expenditure. However I am also interested in
obtaining expenditure elasticities of percapita expenditure on food at
different levels of  total per capita expenditure i.e in my context
d(log(y)/d(log(x)) where x and y are as earlier defined.The problem is
that lpoly does not give estimates of any slope coefficients so I am
at a loss on how to compute these elasticities. I would really
appreciate if anybody could give me advice in this regard.

Thanks,
Nikhil
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