The GADM database of Global Administrative Areas is the place to go for shapefiles of administrative boundaries. The data are freely available for academic use and other non-commercial use. Unfortunately, the boundaries of the Swiss cantons are a bit buggy. Version 2 has fixed the presence of a 27th canton — part of Lake Geneva, but it includes the entire lake of any lake shared with a neighbouring country as Swiss territory.
The licence of the GADM files is never made explicit, and while it says “Please contribute in whatever way you can by sending us a message to point out errors, or even better, to send an improved file for a country of your interest,” there is no way to send improved files on their website. I never got replies to my messages, so consider this post as my sending an improved file.
The files are on Github. I have modified cantonal boundaries so that they match the national boundaries: only the Swiss part of lakes is included as Swiss territory. I’m not sure the files other than the .shp, .shx, .dbf, .prj are actually needed.
Here’s how to draw a map in R. First we load two libraries:
library(sp)
library(rgdal)
Then we import the shapefile:
x <- readOGR(dsn = ".", layer = "ch-cantons")
The dsn argument takes the location of the shapefile (dot for current directory); the layer argument takes the name of the shapefile without extensions.
And now we draw the map:
data <- 1:26 # values to plot
x$data <- data # add to SpatialPolygonsDataFrame
col <- rev(heat.colors(26)) # define colours
spplot(x, "data", col.regions=col, main="", colorkey=TRUE)
The cantons are as follows: c("AG","AR", "AI","BL", "BS", "BE", "FR", "GE", "GL", "GR", "JU", "LU", "NE", "NW", "OW", "SG", "SH", "SZ", "SO", "TG", "TI", "UR", "VS", "VD", "ZH", "ZG").
Didier Ruedin 
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