Rafael,

Your example works for me with raster 2.0-12 (on CRAN). As far as I know
rgeos only gives warnings, not errors, about projections and you could turn
that off with any projection description as it is not interpreted (except
for lon/lat as it will warn about that).

Robert

On Sat, Oct 27, 2012 at 7:09 AM, Rafael Wüest <rafael.wueest@wsl.ch> wrote:

> Dear List
>
> I'm trying to do some image processing with the help of the raster
> package. I'm getting close to what I need. However, the last step involves
> raster::rastreToPolygons, with the option dissolve=T. That's where I'm
> running into an error:
>
> > Error in function (classes, fdef, mtable) : unable to find an inherited
> method for function "proj4string", for signature "NULL"
>
> I figured out that the rgeos function gUnaryUnion is called in the
> background and requires the raster to be projected. Well, my raster is not
> projected, it's a jpeg image. Is there a projection I can use for this or
> does anyone see a workaround?
>
> Here is a small reproducible example:
> library(raster)
> m<-matrix(NA,50,50)
> r<-raster(m,xmn=0,xmx=ncol(m),ymn=0,ymx=nrow(m))
> r[]<-runif(ncell(r),1,100)
> clmps<-clump(r<20)
> polys<-rasterToPolygons(clmps,dissolve=T)
>
> My sessionInfo() output:
> > R version 2.14.2 (2012-02-29)
> > Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
> >
> > locale:
> > [1] de_CH.UTF-8/de_CH.UTF-8/de_CH.UTF-8/C/de_CH.UTF-8/de_CH.UTF-8
> >
> > attached base packages:
> > [1] tcltk     tools     stats     graphics  grDevices utils     datasets
>  methods
> > [9] base
> >
> > other attached packages:
> > [1] rgeos_0.2-7     plyr_1.7.1      stringr_0.6     igraph0_0.5.5-2
> rgdal_0.7-8
> > [6] raster_2.0-08   sp_0.9-99       SciViews_0.9-2  ellipse_0.3-7
> MASS_7.3-17
> > [11] svGUI_0.9-50    svSocket_0.9-53 svMisc_0.9-65
> >
> > loaded via a namespace (and not attached):
> > [1] grid_2.14.2    lattice_0.20-6
>
> Any help is greatly appreciated,
> Rafael
>
>
> --
> Rafael Wüest
> Swiss Federal Research Institute WSL
> Zürcherstrasse 111
> 8903 Birmensdorf
> Switzerland
>
> +41 44 7392126
> rafael.wueest@wsl.ch
> http://www.wsl.ch/info/mitarbeitende/wueest/index_EN
>
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