1

I'm trying to cluster a spatial dataset, and use the cluster labels as an input to a second process. I've been using the spdep package in R.

I've got gridded data at .5 degree lat/lon resolution. There are 19 covariates in the example subset of it linked here

The following shows that I can't calculate the minimum spanning tree -- a necessary input into skater -- when the dataset includes areas undefined because they are over water.

How would one get around this?

system('wget https://www.dropbox.com/s/i72na4k0k5gqvvx/example_data?dl=0')
load('example_data')

    1> with(x, plot(lon,lat))
    1> library(spdep)
    1> bh.nb <- cell2nb(length(unique(x$lon)),length(unique(x$lat)),torus=F,type='queen')
    1> lcosts <- nbcosts(nb = bh.nb, data = x,method='euclidean')
    Error in data[id.neigh, , drop = FALSE] : subscript out of bounds

The points are over the western US and Mexico: enter image description here

If I restrict the data to cut out the missing values, I have no problem:

x = x[x$lon>-117,]
bh.nb <- cell2nb(length(unique(x$lon)),length(unique(x$lat)),torus=F,type='queen')
lcosts <- nbcosts(nb = bh.nb, data = x,method='euclidean')
nb.w <- nb2listw(bh.nb, lcosts, style="B")
mst.bh <- mstree(nb.w,10)
res1 <- skater(mst.bh[,1:2], x, 5)
plot(res1, cbind(x$lon,x$lat), cex.circles=0.035, cex.lab=.7)

and I get this: enter image description here

How do I get around this? I want to be able to cluster the land surfaces, including islands and peninsulas. I suppose that I want islands to be linked to their nearest point of land... but the more I think about islands, the more I'm realizing that's a can of worms.

References as well as fixes to the specific problem with the spdep interface are sought.

  • Hi, have you found a way for clustering your data? I'm facing almost the same question. Thanks. – pacomet Jun 14 '16 at 11:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.