Hi José
Thank you for your reply.
Effectively I'm trying to figure out the theoretical reasons for their use.
Bye
Sebas
At 12.30 01/02/2010, José M. Blanco Moreno wrote:
Dear Seba,
As far as I know, the shape of the kernel is not
that important. Any kernel will yield
approximately the same results as long as the
scaling parameters (bandwidth) are equivalent.
There are some theoretical as well as practical
reasons for choosing finite (compact) kernels -
the practical reasons for big/huge problems become very important ones.
José M.
En/na seba ha escrit:
Maybe I'm getting old...there was something wrong also in the past mail!
Please consider this one.
Sorry for the wrong mails.
Dear list members
I'm always fighting with the decomposition of
trend and residuals or more generally I need to decompose
my signal in high and low frequency
variability. Without coming to wavelets techniques a simple
way is to use moving window averages to obtain
a smoothed signal and removing it from the original
signal to obtain the residuals. In this way the
size of the window let you choose at which level of detail to
perform the analysis, i.e. smaller the window
higher the frequency of the signal you want to study.
But working with moving averages I realize
(well, I know that this is not so a big new!) that performing
moving window simply doing averages gives a
smoothed signal that has some noise; differently if a use some kind
of kernel function (also very simple such the
one used by Grigov et al. "geostatistical
Mapping with continuos moving neighborhood",
mathematical geology vol 36 no. 2, 2004 see
page 273), things work really better (and using
a kernel of that type is like calculating
moving windows averages not on the original
signal but iteratively on moving averages calculated in smaller windows....).
Now my question is: which is the reason for
choosing a specific shape of the kernel????
Sebastiano
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--
---------------------------------------
José M. Blanco-Moreno
Dept. de Biologia Vegetal (Botànica)
Facultat de Biologia
Universitat de Barcelona
Av. Diagonal 645
08028 Barcelona
SPAIN
---------------------------------------
phone: (+34) 934 039 863
fax: (+34) 934 112 842
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