Yes, why didn't I think of that form...?
Anyway, one other useful point to note. You can get a confidence
interval on the position of the maximum from the -nl- function (having
worked out how to express it as a function of the parameters) by using
-nlcom-:
nlcom ln(_b[/delta] / _b[/beta]) / (_b[/beta] - _b[/delta])
David
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Joseph
Coveney
Sent: 11 April 2006 12:26
To: Statalist
Subject: Re: st: finding a peak in an asymmetric curve
The old pharmacokinetics standby (below) seems to do okay for your
example
nl (longevity = {alpha}*exp({beta}*nutrient) + ///
{gamma}*exp({delta}*nutrient)), nolog
display in smcl as result 1 / (-_b[/delta] + _b[/beta]) * ///
ln(_b[/delta] / _b[/beta])
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