Question on symmetric for nb2mat
On Wed, 29 Jul 2020, Andrea Gilardi wrote:
Dear all, I think the following message should work. Excuse me for the
previous message.
library(spdep)
library(rgdal)
library(Matrix)
nc_sids <- readOGR(system.file("shapes/sids.shp", package = "spData"))
Do things in steps: adj <- poly2nb(nc_sids) is.symmetric.nb(adj, force=TRUE) # [1] TRUE
W <- as(nb2mat(adj, style = "B"), "Matrix")
W0 <- nb2mat(adj, style = "B") all(W0 == t(W0)) # [1] TRUE
Matrix::isSymmetric(W) chol(W)
W <- as(W0, "symmetricMatrix") isSymmetric(W) #[1] TRUE res <- chol(W) #Error in asMethod(object) : not a positive definite matrix This step makes little sense - why is it included? I don't know why coercing to Matrix does not see the matrix as symmetric. Or: lw <- nb2listw(adj, style="B") library(spatialreg) W <- as(lw, "CsparseMatrix") #> isSymmetric(W) #[1] TRUE This works and is what you might need: res <- chol((Diagonal(nrow(W)) - 0.1 * W)) or see ?Matrix::USCounties. Roger
If it's still not working I added a reprex here: https://gist.github.com/agila5/59d3a173df9b1efabe13800f748a2d48
Not useful, not in thread nor do any answers stay in thread.
Kind regards Andrea Il giorno mer 29 lug 2020 alle ore 17:19 Roger Bivand <Roger.Bivand at nhh.no> ha scritto:
Please follow-up in this thread posting in plain text (not HTML). As you can see below, HTML garbles your message. On Wed, 29 Jul 2020, Andrea Gilardi wrote:
Dear all, probably I'm missing something obvious but I have a question on the matrix built using nb2mat with argument style = "B". More precisely,
I
don't understand why the following code says that the matrix *W* (which
should be a binary first-order adjacency matrix) is not symmetric:
*library(spdep)library(rgdal)library(Matrix)# datanc.sids <-
readOGR(system.file("shapes/sids.shp", package = "spData"))adj <-
poly2nb(nc.sids)W <- as(nb2mat(adj, style = "B"),
"Matrix")Matrix::isSymmetric(W)#> [1] FALSEchol(W)#> Error in
asMethod(object): not a symmetric matrix; consider forceSymmetric() or
symmpart()*
Kind regards
Andrea
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-- Roger Bivand Department of Economics, Norwegian School of Economics, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no https://orcid.org/0000-0003-2392-6140 https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
Roger Bivand Department of Economics, Norwegian School of Economics, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; e-mail: Roger.Bivand at nhh.no https://orcid.org/0000-0003-2392-6140 https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en