[R] Spatial: number of independent components?

[Nikhil Kaza]

I just updated spdep and I see that as.spam.listw works. Below is  
sessionInfo

Furthermore, it may be straightforward to condense the adjacency  
matrix *before* converting to graph which may help a little bit. You  
can profile the code and see which part needs speeding up.

library(spdep)
library(igraph)

x=matrix(c(0,1,0,0,0,
           0,1,1,0,0,
           0,0,0,0,0,
           0,0,0,1,0,
           0,0,0,1,0),nrow=5)
a <- as.spam.listw(nb2listw(cell2nb(nrow(x),ncol(x),torus=T),  
style="B"))
ind <- which(x>0)
b <- a[ind, ind]
g1 <- graph.adjacency(b)
clusters(g1)$no

---
R version 2.11.1 (2010-05-31)
i386-apple-darwin9.8.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils
[5] datasets  methods   base

other attached packages:
  [1] igraph_0.5.3       spam_0.22-0
  [3] spdep_0.5-11       coda_0.13-5
  [5] deldir_0.0-12      maptools_0.7-34
  [7] foreign_0.8-40     nlme_3.1-96
  [9] MASS_7.3-6         Matrix_0.999375-39
[11] lattice_0.18-8     boot_1.2-42
[13] sp_0.9-64

loaded via a namespace (and not attached):
[1] grid_2.11.1  tools_2.11.1



Nikhil Kaza
Asst. Professor,
City and Regional Planning
University of North Carolina

nikhil.list at gmail.com