On Mon, 12 Feb 2007, Roger Bivand wrote:
> On Mon, 12 Feb 2007, Fernando Mayer wrote:
>
> > Roger, thanks for your explanations. Thanks also to Edzer Pebesma who
> > provided soma additional improvements. However, now I think I have 2
> > problems, as follows:
> >
> > Roger Bivand escreveu:
> >
> > > If you comment out the lines:
> > >
> > > # if(missing(map)) stop("map object is missing.")
> > > # if(!inherits(map, "Map")) stop("Map.obj must be of class Map")
> > > # if(missing(variable)) stop("variable to be plot is missing")
> > >
> > > in ProportionalSymbolMap(), and rename the map argument as verts, you can
> > > pass the coordinates in:
> > >
> > > library(maps)
> > > map <- map("county", "illinois", fill=TRUE, col="transparent", plot=FALSE)
> > > library(maptools)
> > > str(map)
> > > ID <- substring(map$names, 10)
> > > ill <- map2SpatialPolygons(map, ID, proj4string=CRS("+proj=longlat"))
> > > plot(ill, axes=TRUE)
> > > x <- runif(102)
> > > ProportionalSymbolMap_rev(coordinates(ill), x, max.size=0.3)
> >
> > # Problem 1
> >
> > Doing exactly this, I have an error in
> >
> > > plot(ill, axes=TRUE)
> > Error in as.vector(x, "double") : cannot coerce to vector
> >
> > and I was not able to find out what is going wrong. However if I do
> >
> > > map("county", "illinois", fill=TRUE, col="transparent", plot=T)
> >
> > before all that code code and ignore the error, I can see the map with
> > the proportional symbols. So I don't know exactly how long this error
> > influence on what was to be the point here. But, I understood
> > something new here and know comes the
>
> At a distance it's difficult to say - but from #2 below, it doesn't
> matter, because the map is only a background, it does nothing itself.
>
> >
> > # Problem 2
> >
> > As far as I could understand, the polygon IDs are used to identify
> > where the symbols are to be plotted (after the processment with
> > map2SpatialPolygons()). Maybe it was my mistake haven't said this
> > before, but what I'm trying to do is to plot the symbols not in the
> > land, but in the ocean. So I think there's no polygon IDs in this case
> > isn't?
>
> Well, using map() to access boundary data is usually to attach data to the
> polygons, but your case is different, you only need a background. My first
> idea would be to see whether the PBSmapping package already has what you
> need - they are Northern Pacific, but that doesn't have to hurt for your
> South Atlantic location.
>
> I think that I would try to get the coastlines you need from map() or
> Rgshhs() in maptools (possibly with a higher resolution GSHHS database),
> and convert them to a PBSmapping object. The reason for suggesting
> PBSmapping is that the functions provided there are for fisheries
> research, and so may be closer to you than more general functions.
>
> library(maptools)
> gshhs.c.b <- system.file("share/gshhs_c.b", package="maptools")
> SA <- Rgshhs(gshhs.c.b, xlim=c(295,340), ylim=c(-10,-55))$SP
Of course:
SA <- Rgshhs(gshhs.c.b, xlim=c(295,340), ylim=c(-55, -10))$SP
Sorry!
> plot(SA, axes=TRUE, col="grey")
> SA_PBS <- SpatialPolygons2PolySet(SA)
> plotMap(SA_PBS)
>
> I found the map on page 19 of their User Guide quite like what you are
> after, but they choose to colour-fill the quadrats.
>
> The same things can be done with generic sp class objects too.
>
> Roger
>
> >
> > What I'm trying to do exactly is maps to plot fishery data, with the
> > symbols proportional to catch, effort, etc. I was trying something
> > like this [1], which is a function using map(), degAxis(), quantile(),
> > points(), legend(), etc. However I would like to improve this, mainly
> > the legend and the way the symbols are plotted. That's why I was
> > trying the ProportionalSymbolMap(). But now, because of the polygon
> > IDs I'm not sure anymore how this could be done.
> >
> > [1] http://img468.imageshack.us/img468/9397/rplot005us9.png
> >
> > Thanks again for the explanations,
> >
>
>
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: [EMAIL PROTECTED]
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