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From |
Arka Roy Chaudhuri <gabuisi@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: computing elasticities after using lpoly |

Date |
Sat, 6 Oct 2012 03:07:49 -0700 |

Thank you Nick for your advice. However my point in using lpoly is precisely its flexibility. But at the same time I want a measure of the slope of the curve that I get from using lpoly at different points of the curve-so I am not actually looking for one specific number.Rather I am trying to find the slope at different values of my independent variable-so that I can get an idea of the elasticities at different parts of the expenditure distribution. Basically I am trying to implement both Fig 2 and Fig 3 in the following paper (albeit in my context):Deaton, Angus S. and Subramanian, Shankar. "The Demand for Food and Calories," Journal of Political Economy, Feb. 1996,104(1), pp. 133-62 On Sat, Oct 6, 2012 at 2:19 AM, Nick Cox <njcoxstata@gmail.com> wrote: > It seems to me that the whole point of -lpoly- is to be flexible about > modelling a relationship. It has absolutely no sense of any idea of an > overall slope. If you want a number for the slope, -lpoly- is useless. > If you want an independent view of how far the relationship after some > smoothing really is (e.g.) linear or monotonic, then -lpoly- can be > useful, mostly by providing a graph. For what you want, any > appropriate regression method will be better, such as -regress- or > -qreg-. > > Nick > > On Sat, Oct 6, 2012 at 10:06 AM, Arka Roy Chaudhuri <gabuisi@gmail.com> wrote: > >> 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. >> > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: computing elasticities after using lpoly***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: computing elasticities after using lpoly***From:*Arka Roy Chaudhuri <gabuisi@gmail.com>

**Re: st: computing elasticities after using lpoly***From:*Nick Cox <njcoxstata@gmail.com>

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