Question

I am wondering if this is possible to do this R .

I have one data as SpatialLinesDataFrame and another as spatialPolygonDataFrame. Is it possible to overlay these two data ?

When I try to overlay these I get the following error:

  jd <- overlay(res,hello) 
  Error in function (classes, fdef, mtable)  :  unable to find an inherited method for function      
  ‘overlay’ for signature ‘"SpatialLinesDataFrame", "SpatialPolygonsDataFrame"’

In the above code res is the SpatialLinesDataFrame and hello is SpatialPolygonDataFrame.

I have an 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 in “res” extends beyond the shapefile. So I
want to clip that contour with the shapefile and only display the contour
within the shapefile area.

So I am looking for a way to clip the contour layer with the polygon layer.

I have attached the image I got with my code.

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

I also want to know what does overlay does exactly. Does it intersect the area of both the data ?

Thank you.

Answer 1

It sounds like you’re trying to clip your lines to the polygon extent. Use gIntersection from the rgeos package. Here’s a reproducible example:

library(rgeos)
xx <- SpatialPoints(coords=matrix(data=c(0,0), nrow=1))
xx <- gBuffer(spgeom=xx, width=1)
yy <- SpatialLines(list(Lines(Line(matrix(c(-1,1,-1,1), nrow=2)), ID=1)))
zz <- gIntersection(yy, xx)

You can overlay the plot like so:

plot(xx)
plot(zz, add = TRUE, col = "blue")