how to change provincial boundaries and combine two regions

Hi, all
I recently have a problem about Chinese map drawing. The original code as
follows:

*library(maps)
library(mapdata)
map('china')*

This is a China map with provincial boundaries. First, how to change the
boundaries into dashed lines? Second, how to combine two regions (like Xin
Jiang and Tibet) together and create a new bold boundary of this new region
combined by Xin Jiang and Tibet?

?map says:

     ...: Extra arguments passed to ?polygon? or ?lines?.

 and if you read ?lines and ?polygon you'll see that dashed lines can
be drawn using the lty parameter.

map("china",lty=2) will get you dashed lines.

 Your second question is a bit harder. The china data in the mapdata
package seems to not have the region names, and merging regions from
maps package data format might be a bit tricky.

 Try getting China map data in shapefile or RData format from
www.gadm.org - then you can merge areas using some of the functions of
the sp package, or you can do it interactively using a GIS - I
recommend Quantum GIS as a free, open-source package which can do this
kind of editing very easily.

Barry

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