clustering multi band images

On Thu, 12 Jun 2008, Laura Poggio wrote:

Dear list,
I am trying to do some clustering on images. And I have two main 
problems:

1) Clustering multiband images.
I managed to be successful with a single band image, but when trying to
apply to a 3 band I get the following warning message:
In as.matrix.SpatialGridDataFrame(x) :
 as.matrix.SpatialPixelsDataFrame uses first column;
pass subset or [] for other columns


2) saving clustering results as grid or image.
I get a vector of clusters, but without both coordinates. How it is 
possible
to transform it in a grid?

Here the code I use to read the image itself and to do the clustering:

library(rgdal)
fld <- system.file("E:/data/IMG/fr/", package="rgdal")
img <- readGDAL("123_rawR.tif")

kl <- kmeans(img, 5)

img is a SpatialGridDataFrame. kmeans() wants a matrix or data frame, 
so say:

kl <- kmeans(as(img, "data.frame"), 5)