On Mon, 4 Nov 2019, Letícia Dal' Canton wrote:
I am forwarding the routine used and the part of the database I am
interested in, which uses georeferenced agricultural data.
require(spdep)
require(geoR)
dados = read.geodata("test.txt", header = T)
dados
coord=dados$coord
max(dist(coord))/2
grid = dnearneigh(dados$coord, 0, 880)
lw=nb2listw(grid,zero.policy=TRUE)
From this routine, I will try to explain more clearly what my doubts
are:
1) The "dnearneight" function provides the neighbor list object. Is
there any way to numerically visualize who the neighbors are?
"numerically visualize" is not clear. Do you mean "show me who is
neighbour of whom"?
library(spdep)
example(columbus, package="spData")
col.gal.nb # print method for nb objects
print.default(col.gal.nb) # treating nb as a list
col.gal.nb[[1]] # neighbours of observation 1
See also the package vignette vignette("nb_igraph") or:
https://r-spatial.github.io/spdep/articles/nb_igraph.html
https://cran.r-project.org/web/packages/spdep/vignettes/nb_igraph.html
2) The "nb2listw" function provides the "Characteristics of weights list
object". When requesting the weights (lw$w in the routine), the n
points are listed and values are assigned (who are these values?) And
why are not the n values associated to the remaining n-1. Because in
"attr (," comp ") $ d" it is noticeable that each point is associated
to a different amount of points. For example, with the database used,
the first point is associated to another 57, the second to another
65. Why does this occur?
No idea, your data are not available. If you posted HTML, they were
certainly discarded as risky. Post plain text only, and provide data on a
link, not verbatim. If you set the distance threshold to 800, probably
some observations were further than 800 units apart.
all.equal(attr(nb2listw(col.gal.nb)$weights, "comp")$d, card(col.gal.nb))
shows that in this case (row standardisation), the d vector is the same as
the neighbour count per observation - it does not have to be so.
Roger
Thankfully,
Let???cia Dal' Canton.
Matem???tica.
Mestre em Engenharia Agr???cola.
Doutoranda em Engenharia Agr???cola com linha de pesquisa em Estat???stica
Espacial.
Universidade Estadual do Oeste do Paran??? - UNIOESTE.
Curr???culo Lattes: http://lattes.cnpq.br/1085422685501012.
Contato: (45) 9 9962-7492.
[[alternative HTML version deleted]]
--
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: roger.biv...@nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
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