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RE: st: A rose by any other name?


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: A rose by any other name?
Date   Thu, 13 Nov 2008 13:25:18 -0000

As a matter of history, I believe that logistic as a growth curve came
long before the logistic as a CDF, but as Jay implies, between friends
it's the same equation. 

There are some historical references on this within 

SJ-8-1  gr0032  . . . . . . .  Stata tip 59: Plotting on any transformed
scale
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N.
J. Cox
        Q1/08   SJ 8(1):142--145                                 (no
commands)
        tip on how to graph data on a transformed scale

Nick 
n.j.cox@durham.ac.uk 

Verkuilen, Jay

>>To be more precise, the proposed model is a gamma density kernel, not
a
bonafide gamma density ,which integrates on 1.  Of course in this
context, the function is used to model nonlinear trend, not a
probability distribution of some random variable.>>

Right, and thus it's not dissimilar from using the logistic CDF as a
model for growth between asymptotes, which is often done using, say,
Gaussian errors around the curve itself. 


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