[R-sig-Geo] Rgdal and unsigned integers

[Jonathan Thompson]

Dear List,

I use a forest landscape model, which produces 16 bit unsigned ".gis" 
raster files. I often read and manipulate them using rgdal and the 
raster package in R.

However, sometimes, when I read in a unsigned 16 bit .gis, I get the 
following:

stnd <- raster("stand_bm.gis", values = T)

summary(stnd)
Cells:  1474962
NAs  :  0

Values             
Min.    -32140
1st Qu.      0
Median       0
Mean      8316
3rd Qu.  19180
Max.     29620


Where are these negative values coming from?   Opening the same file in 
ArcGIS confirms what I know to be true:

Pixel Type  = unsigned integer
Pixel Depth = 16 bit
Min = 0
Max = 48499

Is there anyway to force raster (or RGDAL) to treat it like an unsigned 
integer?

Thank you,
Jonathan Thompson
Harvard Forest
Harvard University
Petersham, MA 01366