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.htmlhttps://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:

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Roger Bivand

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