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st: fitting a gompertz curve, not in the context of survival analysis


From   Dan Waldo <dan_waldo@yahoo.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   st: fitting a gompertz curve, not in the context of survival analysis
Date   Thu, 28 May 2009 14:56:00 -0700 (PDT)

Dear list members,

I am trying to test whether government revenues as a percentage of GDP can be fit over time with a Gompertz curve -- especially to determine (if the fit is appropriate) the limiting value.

The help I have found comes in the form of survival analysis models, which I have trouble reconciling to the model I am trying to fit.

Is there a Stata add-on that fits Laird's tumor-growth variant of the Gompertz? This would be specified as:

X(t)= K exp(log(X(0)/K)exp(-at))

where X is known and K and a are estimated.

Thanks in advance for any tips.

Dan Waldo


      
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