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

[Dan Waldo <dan_waldo@yahoo.com>]

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


      
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/