[R] Finding local maxima on a loess surface

[David Winsemius]

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