Add lines from SpatialLinesDataFrame to an image of SpatialGridDataFrame

On Thu, 22 Jun 2006, Andy Bunn wrote:

Howdy all: I have a simple question. Given two sp objects, a
SpatialGridDataFrame tdmean and SpatialLinesDataFrame states I 

want to plot

tdmean as an image and draw the lines on top. Can this be done with sp?

class(tdmean)

[1] "SpatialGridDataFrame"
attr(,"package")
[1] "sp"

is.projected(tdmean)

[1] TRUE

class(states)

[1] "SpatialLinesDataFrame"
attr(,"package")
[1] "sp"

is.projected(states)

[1] TRUE

# plot states and put the image on top: works but is unsatisfying
plot(states,axes=T)
image(tdmean["z"],add=T)

# plot image and put the state lines on top: doesn't work
image(tdmean["z"],axes=T)
lines(states)

Cany you please try:

image(tdmean, "z", axes=T)
plot(states, add=TRUE)

I don't think there is a lines() method for SpatialLines* objects.

Roger

-- 
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