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st: nlcom command for elasticity


From   HENRY AKAEZE <akaezehenry@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: nlcom command for elasticity
Date   Thu, 3 Jun 2010 06:39:34 -0700 (PDT)

Dear Statalisters,

I am doing estimation using the AIDS model. In order to estimate elasticity, I used nlcom command on an elasticity function I derived through differentiation as follows:

nlcom((-.0093/cpi)*((gdpca/cifprice1)-$b*(lagimportca-$a*laglocalca))*8.89)

The exogenous variables are CPI, CIF and the lags of import and domestic products.

However, stata complained that reference was made to X rather
than _b[X] as follows:



expression((-.0093/cpi)*((gdpca/cifprice1)-.6892200041267298*(lagimportca-.1785226557738297*laglocalca))*8.89)
contains  reference to X rather than _b[X]

When evaluated at their means I got a value but without standard errors and p-value as below:

  nlcom((-.0093/35)*((36/.33)-$b*(3.7-$a*14.4))*8.89)

  _nl_1:(-.0093/35)*((36/.33)-.6892200041267298*(3.7-.1785226557738297*14.4))*8.89



------------------------------------------------------------------------------

    importca
|             
P>|t|      Coef.                              [95% Conf. Interval]
                       Std. Err.      t
-------------+----------------------------------------------------------------
_nl_1 -.255856          .              .                   .     
                     

------------------------------------------------------------------------------

  Could anyone help me out please. I need to know what is going on and what I must do to get values for the standard errors,  t-stat and conf. interval.

Thank you,

Henry


      
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