[R] Retrieve Axis coordinates from map

[David Winsemius]

On Jul 24, 2014, at 2:05 PM, Julien Million wrote:

> Hi, 
> 
> i want to automatise the creation of some maps with R, however, I would need
> to be able to retrieve the coordinates of the axes that R is automatically
> generated. 
> 
> When using the package MAPS,

Case matters in R so this is the wrong spelling.

> and creating a map, R will automatically adjust
> the plot to the region that you are plotting.
> 
> for example the two command:
> map(regions="Morocco")
> or 
> map(regions="France")
> will generate plots with completely different axis and scale. If I want to
> automatically generate a map and add a legend to it, I would need to be able
> to retrieve the coordinates of my axis that were automatically generated in
> order to give coordinate to place my legend on the map.
> 
> Basically I would like to automatise the following with a function, and be
> able to automatically get the coordinates for my legend)
> 

require(maps)
> map(regions="Morocco")
> map.axes()
> legend(-12,34, "blablabla")

Perhaps something like this:
legend(-12,35.5, paste( paste("Xrange = ", round( par("usr")[1:2],2), collapse=" "), 
                        paste( "Yrange = ", round( par("usr")[3:4],2) , collapse=" "),
                        sep="\n")  )

?par  # since pkg::maps uses base graphics.

> 
> map(regions="France")
> map.axes()
> legend(-150,40, "blablabla")
> 
> mapcountry <- function(country) {
> map(regions=country)
> map.axes()
> legend(xxxx, yyyy, "blablabla")
> }
> 
> I want to be able to extract the xxxx and yyyy automatically to be able to
> generate the legend within the function.
> 
> Thanks
> 
> Julien
> 
> 
> 
> 	[[alternative HTML version deleted]]

r-help is a plain text mailing list.
> 
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html

And thank you for providing working code.
-- 
David Winsemius
Alameda, CA, USA