Message-ID: <AE59C429-B397-40DC-8FBE-F4ECF80DC3C8@comcast.net>
Date: 2012-05-05T14:34:33Z
From: David Winsemius
Subject: Finding local maxima on a loess surface
In-Reply-To: <CAGxpRUqqDHs7gaSUndKeYGUkF4j19GP-UsX05b9FTWWG_xX-QA@mail.gmail.com>
On May 4, 2012, at 3:00 PM, Diego Rojas wrote:
> Thanks, I know about it but i wat to find several local maxima, so
> in other words I need a way to identify the places in the surface
> where both slopes are equal to 0 and the second derivative is
> negative.
There is no way that I know that will produce a mathematical function
that would support symbolic manipulations of that sort for the results
obtainable from a loess-object. I was expecting that you would be
approaching this numerically and doing evaluations on a grid. Testing
for equality to 0 is not a good practice if following that route. Sign
reversal would be a more sensible criterion. ( And you _would_ be
using predict.loess(). )
Still no data example or code offered, so not pursuing further efforts
at illustration.
>
> On Fri, May 4, 2012 at 9:28 AM, David Winsemius <dwinsemius at comcast.net
> > wrote:
>
> On May 3, 2012, at 6:09 PM, Diego Rojas wrote:
>
> If a run a LOESS model and then produce a smoothed surface: Is there
> any
> way to determine the coordinates of the local maxima on the surface?
>
> ?predict # it has a loess method.
>
> [[alternative HTML version deleted]]
>
David Winsemius, MD
West Hartford, CT