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st: Using nlcom for computing elasticity
From 
 
HENRY AKAEZE <[email protected]> 
To 
 
[email protected] 
Subject 
 
st: Using nlcom for computing elasticity 
Date 
 
Thu, 3 Jun 2010 06:14:03 -0700 (PDT) 
Dear Members,
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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