delete region from shapefile / map only certain regions

Hello,
I have two qeustions about shape files:

First, I have a shp.file for all counties in Germany. Funnily enough,
two counties are just lakes for which
    I do not have covariates. Is there a possibilty delete them, so
they don't show on the map and do not affect my analysis.

Second, is it possible just to plot parts of the map, given some
condition (say, part of a state or a larger region)?

I hope these question are not too trivial, but I couldn't find
anything adequate in the mailing list.
Happy new Year,
Stefan

Hello Stefan,

answering only to your first question.

On 05.01.2008 22:38 (UTC+1), stefan lhachimi wrote:

Hello,
I have two qeustions about shape files:

First, I have a shp.file for all counties in Germany. Funnily enough,
two counties are just lakes for which
    I do not have covariates. Is there a possibilty delete them, so
they don't show on the map and do not affect my analysis.

I am not sure what you mean with 'lakes'. Is it possible, that this
polygons describe the mini counties (~ cities with municipal laws like
counties) 'Hamburg' and 'Bremen' both in the northern part of Germany?
If so, I would suggest to not delete them.

Hope this helps,
Rainer

Second, is it possible just to plot parts of the map, given some
condition (say, part of a state or a larger region)?

I hope these question are not too trivial, but I couldn't find
anything adequate in the mailing list.
Happy new Year,
Stefan

Hello,
I have two qeustions about shape files:

First, I have a shp.file for all counties in Germany. Funnily enough,
two counties are just lakes for which
   I do not have covariates. Is there a possibilty delete them, so
they don't show on the map and do not affect my analysis.

Second, is it possible just to plot parts of the map, given some
condition (say, part of a state or a larger region)?

I hope these question are not too trivial, but I couldn't find
anything adequate in the mailing list.
Happy new Year,
Stefan

On Sat, 5 Jan 2008, stefan lhachimi wrote:

Hello,
I have two qeustions about shape files:

First, I have a shp.file for all counties in Germany. Funnily enough,
two counties are just lakes for which
   I do not have covariates. Is there a possibilty delete them, so
they don't show on the map and do not affect my analysis.

If you use readShapePoly() in maptools, they will be read into a
SpatialPolygonsDataFrame object. You subset it using "[" as other data
frame objects - see the examples in ?readShapePoly, and more class
documentation in the sp package. Create a logical vector to do the
subsetting.

Second, is it possible just to plot parts of the map, given some
condition (say, part of a state or a larger region)?

Either subset in the same way (counties in a land, for example), or use
the xlim= and ylim= arguments to the plot() or spplot() methods for the
class, depending on what you need. For plot(), you need to set the class
intervals for colour filling yourself, for spplot() you can set up a
legend and class intervals automatically.

Hope this helps,

Roger

I hope these question are not too trivial, but I couldn't find
anything adequate in the mailing list.
Happy new Year,
Stefan

--
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