[R-sig-Geo] Overimposing one map in ssplot onto another

[Roger Bivand]

On Fri, 27 Jan 2012, Dimitri Liakhovitski wrote:

> Hello!
>
> I have 2 maps - both created in ssplot and both identical in terms of
> outline. Is there any way to superimpose Map1 (which has black borders
> between Canadian provinces) onto Map2 (which is also a map of Canada)?
> Thanks a lot for your hints!

See the sp.layout= argument to spplot() - here:

spl <- list("sp.lines", as(can1, "SpatialLines"), lwd=0.4)

should give what you need, as lines plot over polygons, but not the 
opposite.

Roger

> Dimitri
>
> ### A. Reading in Canada data at the province and then at the county level:
> library(raster)
> getData('ISO3')  # Canada's code is "CAN"
> can1<-getData('GADM', country="CAN", level=1)
> can2<-getData('GADM', country="CAN", level=2)
>
> ### B. Creating Map1- with borders between provinces:
> can1 at data[["groups"]]<-1   # want all provinces to have the same
> color, but ideally I'd like the whole map to be transparent.
> can1 at data$groups<-as.factor(can1 at data$groups)
> spplot(can1,zcol="groups",col.regions="white",colorkey = FALSE,
> lwd=.4,  # col='white',
>  par.settings = list(axis.line = list(col='transparent')))
>
> ### C. Creating Map2- with borders between colored counties:
> # Creating an (artificial) grouping of Canadian admin units:
> nrofunits<-length(can2$NAME_2)
> groups<-c(rep(1:6,(nrofunits %/%
> 6)),rep(1,5))[order(c(rep(1:6,(nrofunits %/% 6)),rep(1,5)))]
> # adding values (grouping values) to "data":
> can2 at data[["groups"]]<-groups
> can2 at data$groups<-as.factor(can2 at data$groups)
> classcolors <- rainbow(6)
> spplot(can2,zcol="groups",col.regions=classcolors,colorkey =
> FALSE,lwd=.4,col='white',
>  par.settings = list(axis.line = list(col='transparent')))
>
> --
> Dimitri Liakhovitski
> marketfusionanalytics.com
>
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
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