[R-sig-Geo] Adding some data as colors to world map

[Roger Bivand]

On Sat, 11 Mar 2006, Gregor Gorjanc wrote:

> Hello!
> 
> I appologize for my absence but I was completely stuffed with my work in
> last days. I would like to express thanks to all who took their time and
> showed various ways how to accomplish my task. I did not expect to get
> so many valuable responses. I will plot data from FAOSTAT database
> http://faostat.fao.org/faostat/collections?subset=agriculture
> 

Using world_countries.rda (see below for access) and matching against a 
short sample csv from FAO (they don't seem to give access to more than 25 
line samples without registration) - sample for Oceania:

> world_countries$ISO3166[match(toupper(as.character(oc_aa$Country)), 
as.character(world_countries$names))]
 [1] AS   AU   CK   <NA> PF   GU   KI   MH   <NA> NC   NZ   NU   NF   <NA> PW  
[16] PG   WS   SB   TO   TV   VU   <NA>
230 Levels: AD AE AF AG AI AL AM AN AO AR AS AT AU AW AZ BA BB BD BE BF ... ZW

looks promising - you'll still have a bit of manual editing to add the 
ISO3166 codes to the FAO data. But it can be done once-off, I guess, as 
you said.


> ...
> > 
> > 
> > I've produced a world map with ISO3166 two-letter codes. To get your
> > codes right - this lists out country names and codes:
> > 
> > as(world_countries, "data.frame")
> > 
> 
> OK, I will need to do the mapping, since FAO uses full names for
> countries, but that is a minor problem. I will just create a list of
> mappings and apply it.
> 
> > then
> > 
> > countries <- c("AU", "US", "AR") colours <- c("blue", "red", "green")
> >  plot(world_countries, col=colours[match(world_countries$ISO3166,
> > countries)])
> > 

The classInt package new on CRAN can help, if you like, with choosing 
colours for the polygons or bubbles.

> 
> Very clean and nice solution. I like it. If I would also go for bubbles,
> how can I determine the position where to put the bubble on i.e. "the
> center" of the country?

symbols(coordinates(world_countries), ...)

should do it. Have a look at Susumu Tanimura et al. in JSS 2006 for a nice 
discussion of symbol size.

> 
> > gives the attached PNG. Shall I make an .RData file of the 
> > SpatialPolygonsDataFrame object available?
> 
> Yes, please do.

On:

http://spatial.nhh.no/R/etc/world_countries.rda

now, please let me know if it works for you. Please use library(sp) to 
define the loaded object.

> 
> Many thanks again!!!
> 
> P.S. In one of previous posts you mentioned
> > The advantage of the sp class representation here is that we can
> > project the data to make areas more comparable if you need that,
> > otherwise Greenland, Russia, and Canada dominate totally!
> Can you please elaborate a bit further on this topic since I do not
> follow it fully. Perhaps you can show on above example.
> 

The specific choice of the projection depends on which part of the world 
you want to present, and on other cartographic criteria. This is a good 
reference:

http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html

but there are thousands of interesting choices, I'm afraid. Projection is 
supported in the newest version of rgdal on CRAN using the transform() 
method, but you need to know which coordinate reference system to go to. 
If there is a typical projection used in your field, it should be 
identifiable, and can then be done to make a projected basemap.

> P.P.S. Did you "get any further" with Giovanni's tutorial and recent
> changes in maptools?
> 

Not yet, but it'll come before too long!

Best wishes,

Roger

> 

-- 
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: Roger.Bivand at nhh.no