Hi!

I have an issue with interpretation of the results of "rhohat" function
(spatstat package). I use a classified raster as a covariate to my point
process. A raster is a land cover image with 300 m resolution. There are
several classes with values like 10, 20, 50, 100 etc. - all are multiple of
10.

The result of rhohat (http://image.bayimg.com/fapcmaadf.jpg) demonstrates
two peaks at values 135 and 165. Despite the fact that all raster values
are multiple of 10 and so there are no such values as 135 and 165, there
are also no such values as 130, 140, 160 or 170 (see histogram:
http://image.bayimg.com/fapcpaadf.jpg).

So the question is what did I get and why? And is it correct to use a
classified raster as a covariate in "rhohat"?

Here is the code (P is a ppp):

> gl <- readAsciiGrid("/some_path/land_cover.asc", as.image=TRUE,
>      proj4string= CRS("+proj=tmerc +lat_0=0 +lon_0=33 +k=1 +x_0=6500000
> +y_0=0 +ellps=krass

                            +towgs84=23.92,-141.27,-80.9,-0,0.35,0.82,-0.12
> +units=m +no_defs"))

glim <- as.im(gl)
> plot(rhohat(P, glim, covname="LandCover"),
>  xlab= "Global Land Cover",
>  legendpos = "topleft",
>  legendargs=list(bg="transparent"),
>  main = NULL)


Best regards,
Yury Ryabov

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