Stata The Stata listserver
[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: non-linear least squares


From   "Metcalfe, Paul" <Paul.Metcalfe@nera.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: non-linear least squares
Date   Wed, 26 Nov 2003 11:58:31 -0000

Dear statalisters,
A colleague of mine has asked for help with the following stata query:

Working with non-linear least squares regression, Stata 8 includes a couple of non-linear functions already programmed.  The logistic function:
	nl log3    Y = b1/(1 + exp(-b2*(X-b3)))
and the Gompertz:
	nl gom3    Y = b1*exp(-exp(-b2*(X-b3)))

However, looking at various econometric manuals, these functions are normally of the form:
	log        Y = b1/(1+(b2*exp(-b3*X)))
      gom        Y = b1*exp(-b2*exp(-b3*X)))

I can't find a mathematical way to move between the two; are the functions programmed into Stata a recognised alternative form, or is the help file incorrect?

Regards,
Paul 
  
  
_____________________________________________________________ 
  
This e-mail and any attachments may be confidential or legally privileged. If you received this message in error or are not the intended recipient, you should destroy the e-mail message and any attachments or copies, and you are prohibited from retaining, distributing, disclosing or using any information contained herein. Please inform us of the erroneous delivery by return e-mail.  
 
  
Thank you for your cooperation. 
  
_____________________________________________________________ 
  
 

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index