Dear Simon.
thanks for the tip, now it works fine
best
marco

2012/10/30 O'Hanlon, Simon J <simon.ohanlon@imperial.ac.uk>

> Dear Marco,
> You can download shapefile of the world in varying resolutions at
> http://www.naturalearthdata.com/ Check under the links marked 'cultural'.
>
> They  come with country boundaries but I think you can easily melt these
> using rgeos:::gUnaryUnion
>
> Thanks,
>
> Simon
>
> -----Original Message-----
> From: r-sig-geo-bounces@r-project.org [mailto:
> r-sig-geo-bounces@r-project.org] On Behalf Of marco milella
> Sent: 29 October 2012 22:12
> To: r-sig-geo
> Subject: Re: [R-sig-Geo] kriging limits
>
> Dear Rob,
>
> thanks for the help. However, my shp file is a SpatialLinesDataFrame, so
> things not work (blue plot). On the other hand, I tried with an old map of
> Europe (SpatialPolygonsDataFrame) and it works fine. Do any of you know
> where to find SpatialPolygonsDataframe .shp file of all world (possibly
> without coutries boundaries)?
> Thanks in advance for any feedback
> marco
>
> 2012/10/29 Rob Robinson <rob.robinson@bto.org>
>
> > Marco,
> >  'colouring' only the land is relatively easy, kriging over just the
> > land is much harder... To do the former, all you need to to do is plot
> > your kriged map, then plot a 'mask' over the sea area. To create the
> > mask, you need something like the snippet below
> >
> > world<-readShapeSpatial("10m_coastline.shp")
> >
> > library(rgeos)
> > g3<-readWKT("POLYGON((-180 -90,-180 90,180 90,180 -90,-180 -90))")
> > sea_mask<-gDifference(g3,world)
> > plot(sea_mask, col='blue', border='transparent', add=T)
> >
> > hope that helps
> > cheers
> > rob
> >
> >
> >
> > **************  Find out about Britain's birds - www.bto.org/birdfacts
> > **************
> >
> > Dr Rob Robinson, Principal Ecologist
> > British Trust for Ornithology, The Nunnery, Thetford, Norfolk, IP24 2PU
> > Ph: +44 (0)1842 750050     E: rob.robinson@bto.org
> > Fx: +44 (0)1842 750030     W:
> www.bto.org/about-bto/our-staff/rob-robinson
> >
> > ====== "How can anyone be enlightened, when truth is so poorly lit"
> > =======
> >
> >
> >
> >
> > On 28 October 2012 13:25, marco milella <vrukol@gmail.com> wrote:
> >
> >> Dear all,
> >>
> >> I'm a relatively new with R. However, I realized from colleagues the
> >> great capabilities of R or analyzing geo data.
> >> I'm interested in performing an ordinary kriging to interpolate z
> >> value on a world map sarting from a dataset that (unfortunately)
> >> includes rather few observations (13 locations worldwide).
> >> my problems are the following:
> >>
> >> 1) the obtained plot extend the kriging to seas and i would like to
> >> "color"
> >> only lands
> >> 2)I can't find a way to illustrate the kriging in a more "wave (or
> >> bands) of colors rather that in a extremely smooth way as you see in
> >> the attached figure
> >>
> >>
> >>
> >> below my commands
> >>
> >>   library(maptools);library(fields);library(maps);library(geoR)
> >> #here I import a .shp file representing world coastlines downloaded
> >> from http://www.soest.hawaii.edu/pwessel/gshhs/index.html
> >>   world<-readShapeSpatial("10m_coastline.shp")
> >> #now I import my dataset (value.txt), including 13 rows (each
> >> location) and
> >> 3 columns (Lat, Long, value)
> >>   dati<-read.table("value.txt",header=TRUE)
> >>   attach (dati)
> >>   s<-cbind(Long,Lat);
> >>   ml <- likfit(data=dati[,3],coords=s,
> >>                fix.nugget=F,cov.model="exponential",
> >>                ini = c(30, 5),nugget=5);
> >>   sp1<-seq(min(s[,1]),max(s[,1]),length=500);
> >>   sp2<-seq(min(s[,2]),max(s[,2]),length=500);
> >>   sp<-expand.grid(sp1,sp2);
> >>   inCA<-map.where("state",x=sp[,1],y=sp[,2]);
> >>   inCA<-inCA=="world"
> >>   pred<-krige.conv(data=dati[,3],coords=s,locations=sp,
> >>                    krige=krige.control(cov.model="exponential",
> >>                                        cov.pars=c(26.19,13.7),
> >>                                        nugget=4.5763));
> >>   image.plot(sp1,sp2,matrix(pred$predict,500,500),zlim=range(dati[,3]))
> >>   map("world",add=T)
> >>
> >>         [[alternative HTML version deleted]]
> >>
> >> _______________________________________________
> >> R-sig-Geo mailing list
> >> R-sig-Geo@r-project.org
> >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>
> >
> >
>
>         [[alternative HTML version deleted]]
>
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>

	[[alternative HTML version deleted]]

