[Portugal] Kernel Density

[Eloi Ribeiro]

On Wed, Dec 16, 2009 at 7:19 PM, Giovanni Manghi
<giovanni.manghi  gmail.com>wrote:

> Viva,
>
>
> > > Estou a precisar construir um raster através da ferramenta de Kernel
> > > Density baseada numa layer de pontos e num dos seus atributos. Já
> > > estive a experimentar no gvSIG+Sextante e o resultado não me
> > > satisfaz uma vez que só me aceita pixel de 1000 metros. Se diminuir
> > > este parâmetro tenho problemas com Java Heap Space (memória). Fui ao
> > > grass dentro do qgis e vejo la a função gaussian kernel mas não
> > > permite seleccionar um atributo do vector. Alguém tem sugestões???
> > >
> > > Obrigado.
> > > Abraço Viva,
>
>
>
> no QGIS poderá usar o plugin
> "SDA4PP" (Spatial Data Analysis for Point Pattern) que, entre as outras,
> inclui as seguintes ferramentas:
>
>
>                      * Interactive Identify Tool: returns the value of
>                        overlapping raster and vector layers at the same
>                        time in one window. It gives more information
>                        about feature than the standard identify tool in
>                        QGIS.
>                      * Quadrat analysis: A method of point pattern
>                        analysis in which the study region is sampled
>                        using a set of similar shapes (quadrats) and
>                        counting the number of events in each. Analysis
>                        of the resulting quadrat counts can help
>                        determine whether the pattern is evenly spaced
>                        or clustered.
>                      * F function: A function in point pattern analysis
>                        based on the cumulative frequency of the
>                        shortest distance between events in a point
>                        pattern and a set of randomly placed locations
>                        in the study area.
>                      * G function: A function in point pattern analysis
>                        based on the cumulative frequency of the
>                        shortest inter- event distances between events
>                        in a point pattern.
>                      * K function: A function in point pattern analysis
>                        based on all the inter-event distances between
>                        events in a point pattern.
>                      * Kernel density estimation: A method of density
>                        estimation making use of kernel functions. For
>                        each event to be included in the density
>                        estimates a kernel function is used to 'spread'
>                        its effect across space.
>
>
> http://ggit.metu.edu.tr/~volkan/screenshots.html<http://ggit.metu.edu.tr/%7Evolkan/screenshots.html>
>
> Para o plugin funcionar é necessario instalar o pacote estatístico "R" e
> algumas suas bibliotecas adicionais.
>
> Saluti
>
> --
> Giovanni Manghi
> Faunalia.pt
> Sistemas de Informação Geográfica Open Source
> Portugal
>
> Web: http://www.faunalia.pt
> Email & Jabber: giovanni.manghi  faunalia.pt
> PGP Key available
> Tel. + 351 96 7058216
> --
>
>
Para utilizar "SDA4PP" (Spatial Data Analysis for Point Pattern) é
necessário intalar, entre outras coisas, *python-rpy2* e depois os pacotes
de R *sp*, *rgdal*, *maptools*, *spatstat*. Acontece que nao consigo
instalar *spatstat*, da-me:

> install.packages("spatstat", dependencies=TRUE)
Warning in install.packages("spatstat", dependencies = TRUE) :
  argument 'lib' is missing: using
'/home/eloi/R/x86_64-pc-linux-gnu-library/2.9'
--- Please select a CRAN mirror for use in this session ---
Loading Tcl/Tk interface ... done
Warning message:
In getDependencies(pkgs, dependencies, available, lib) :
  package ‘spatstat’ is not available

Alguma ideia do porque? Estou com Ubuntu 9.10.


-- 
Eloi Ribeiro
GIS Analyst
39.45º -4.40º
http://eloiribeiro.wordpress.com
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