[R-sig-Geo] clustering multi band images

[Roger Bivand]

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)

Then

img$cluster <- kl$cluster

image(img, "cluster")

Does this help?

Roger

>
> I am quite new to image processing, especially within R, and any help is
> greatly appreciated.
>
> Thank you in advance
>
> LP
>
> 	[[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

-- 
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: Roger.Bivand at nhh.no