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# st: nlcom for elasticity in nonlinear least squares

 From HENRY AKAEZE To statalist@hsphsun2.harvard.edu Subject st: nlcom for elasticity in nonlinear least squares Date Tue, 1 Jun 2010 06:10:14 -0700 (PDT)

```Hello,
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          .              .                   .

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

WHAT COULD POSSIBLE BE WRONG AND WHAT DO I NEED TO DO TO OBTAIN A COMPLETE RESULT?

Thank you,

Henry

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