[R-sig-Geo] How to clip the object created by Conourlines2SLDF with polygon

[jdbaba]

Hello All,

I am a new user in R and am trying hard to have a understanding in R and
mapping techniques. 

I have an estuary shapefile and then I have data points with x,yand z
coordinates. I want to show the contour lines on the shapefile. 

The procedure I used is using akima package to do the interpolation. The
code I used to interpolate is 

fld <- interp(x,y,z)

Then I changed this to spatial object by using following code:

res <-ContourLines2SLDF(contourLines(fld))

The above command would store the contourlines as spatial data. 

Then I read the shapefile and I plot both shapefile and res as follows:

p1 <-
spplot(hello,sp.layout=list(list("sp.lines",res)),col="blue",lwd=0,fill="grey",colorkey=F)
p1

"hello" is my shapefile and "res" is the object I created as shown above. 

The problem is contour stored is "res" extends beyound the shapefile. So I
want to clip that contour with the shapefile and only display the contour
within the shapefile area. 



I have attached the image I got with my code. 
<http://r-sig-geo.2731867.n2.nabble.com/file/n7582339/shapefile_with_contour.png> 


In the image you can see the lines out of the shapefile. I also want to know
how can I display the contour levels on the map. 

Thank you so much. 

Jdbaba



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