On Thu, 7 Oct 2010, Gabriele N. wrote:
Hy everyone.
I have a raster which is the result of calculating an index of remote
sensing (with decimals).
I would like to calculate the Moran's index and the index of Getis and Ord
To do this I installed R (following
http://grass.fbk.eu/statsgrass/grass6_r_install.html).
Then I installed the packages
install.packages("spdep",dependencies=TRUE)
install.packages("maptools",dependencies=TRUE)
Then from the shell:
R
Then load these libraries
library(spgrass6)
library(spdep)
library(maptools)
library(boot)
library(Matrix)
library(lattice)
I read the raster
index_water_2009<-readRAST6("index_water_2009")
At this point I stopped. I saw on the mailing list and some tutorials.
I can not understand the syntax to use.
Well, in rasters the number of "observations" is typically very large,
probably artificially so, depending on the "natural" resolution of the
phenomena of interest. Consequently, in rasters one almost always finds
strong positive spatial autocorrelation, because the cells do not
represent well the actual entities. If you need to do this, you can try
in Spearfish:
library(spgrass6)
gmeta6()
execGRASS("g.region", parameters=list(res="150"))
# to coarsen the input resolution
gmeta6()
elev <- readRAST6("elevation.dem")
GT <- slot(elev, "grid")
library(spdep)
nb_rook <- dnearneigh(coordinates(elev), 0, mean(slot(GT,
"cellsize"))*1.05)
summary(elev)
# note NAs, need to subset to handle:
mt <- moran.test(elev$elevation.dem, nb2listw(nb_rook), na.action=na.omit)
# using spatial weights row standardisation
mt
Hope this helps,
Roger
It only works on vector?
Someone can give me some help?
Thanks
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: [email protected]
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