Here's what I tried. I can plot a selection of regions, but I
can't seem to remove an arbitrary list of region numbers, unless I've done
something wrong
by selecting the regions I want to plot with departements[-exclude].
I also get an error
when I try to use map.text to label a map with only the regions I'm
selecting.
departements <- map('france',namesonly=T, plot=FALSE)
# returns a vector of names of regions
exclude <- c(47, #Alpes-Maritimes
+ 66, # Haute-Savoie
+ 76, # Savoie
+ 95, # Territore-de-Belfort
+ 109, 110, 111, # Var: Iles d'Hyeres
+ 49, 53, 54, 55, # Moribhan: Isles
+ 62, 64, # Vendee: Isles
+ 72, 75 # Charente-Maritime: Isles
+ )
depts <- departements[-exclude]
gfrance <-map('france', regions=depts)
labels <- (as.character(1:length(departements)))[-exclude]
gfrance <-map.text('france', regions=depts, add=FALSE, labels=labels)
Error in map.text("france", regions = depts, add = FALSE, labels = labels) :
map object must have polygons (fill=TRUE)
Another problem, potentially more difficult for mapping data on the map of
France is that
the "departements" are actually just the polygons in the map, arbitrarily
numbered from
east to west, and from north to south --- they don't correspond to the
'official' administrative
region numbers. As well, the departement names don't always match exactly
(ignoring
accents, e.g., Val-d'Oise vs. Val-Doise) so it would be another challenge
to plot my
historical data on the map of France.
-Michael
Stephane DRAY wrote:
Hello. I do not know if you can merge polygons, but you can select easily:
departements=map('france',namesonly=T) # returns a vector of names of
map('france',regions=departements[1:20],namesonly=T) # use what you
need with regions argument
Hope this helps,
At 16:29 18/11/2004, Michael Friendly wrote:
I'm doing some analyses of historical data from France in 1830 on 'moral
statistics' that I'd like to
show on a map. I've done most of my analyses in SAS, but a few things
would work better in R.
To do this, I have to adjust the modern map,
library(maps)
map('france')
to adjust for changes in departments (86 in 1830, to 97 now). I've read
the documentation
for the maps and maptools package, but there seems to be no functions to
allow this, and
I can't find information on the exact structure of map datasets, but I
understand them to
be delimited lists of polygon coordinates.
In SAS, all maps have (one or more) ID variables representing the
geographical region,
and there is also a proc gremove that can remove internal boundaries
inside the polygons
for regions with the same ID. Is there some way I can do this in R?
Here's what I did in SAS:
*-- Fix the map of France to conform to Guerry:
- adjust the 97 current departments to correspond to the 86 in 1830
- delete those not part of France then
;
data gfrtemp;
set maps.france;
/* Corse was one dept - merge these to one area, new ID */
if id in (201, 202) then dept=200;
/* Seine et Oise (78) was cut into
Essonne (91), Val d'Oise (95) and Yvelines (78) */
else if id in (91, 95) then dept=78;
/* Seine (75) now split into
Hauts-de-Seine (92), Seine-Saint-Denis (93) et Val-de-Marne (94)*/
else if id in (92, 93, 94) then dept=75;
/* departments not part of France in 1830 */
else if id in (
6, /* Alpes-Maritimes */
73,74, /* Savoie, Haute-Savoie */
90) /* Territore-de-Belfort */
then delete;
else dept=id;
run;
*-- remove internal boundaries based on merged DEPT;
proc sort data=gfrtemp;
by dept;
proc gremove data=gfrtemp out=gfrance;
by dept;
id id;
run;
--
Michael Friendly Email: friendly at yorku.ca Professor, Psychology Dept.
York University Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT M3J 1P3 CANADA