Dear Michael,

Thank you so much for the help.  What I ended up doing was this:
image(x2009.final)
addPolys(worldLLhigh)

So obvious is hindsight but most of these things are.  Thank you again for
the help.
All the best -- Trevor



On Mon, Mar 10, 2014 at 8:27 PM, Michael Sumner <mdsumner@gmail.com> wrote:

> Hi, this doesn't have much to do with tripGrid, since the object to
> plot is just a SpatialGridDataFrame.
>
> I don't use PBSmapping, so I haven't looked at that - perhaps there is
> an add = TRUE option to plotMap (?), so perhaps you could do this:
>
> image(x2009.final)
> plotMap(..., add = TRUE)
>
> Your main issue may be that you are using the Pacific view (0, 360)
> longitudes rather than (-180,180).  I don't know how/if plotMap deals
> with that,
>
> Otherwise, I would use a different data set and just use the sp plot
> functions.
>
> image(x2009.final)
> library(maptools)
> data(wrld_simpl)
> plot(elide(wrld_simpl, shift = c(360, 0)), add = TRUE)
>
> You need to "elide" it to shift it 360 in longitude since your range
> is c(292,303.5)
> The same will work with other polygon data in longlat read with
> rgdal::readOGR or maptools::readShapePoly. To actually crop wrld_simpl
> you can use "[" with matches on the data attributes, or use
> rgeos::gIntersection.
>
> You also could modify your input data to be in the range -180,180, or
> use a map projection before using the trip* functions.
>
> I know there's a lot of options listed above, but it really does
> depend on which aspects matter to you.
>
> HTH
>
>
>
> On Tue, Mar 11, 2014 at 10:09 AM, Trevor Davies <davies.trevor@gmail.com>
> wrote:
> > Hello,
> >
> > Sorry for the lack of a complete example but this is more of a class type
> > question.
> >
> > I have a map of the coast that I generated through PBSmapping:
> >
> > xlims <- c(292,303.5)
> > ylims <- c(41.5,49.5)
> > plotMap(worldLLhigh, xlim=xlims, ylim=ylims, col=grey(0.1),bg=grey(0.9),
> > xlab="", ylab="", las=1, tck=-0.015, axes=F)
> >
> > I want to add an intensity grid from an object that I created through the
> > excellent 'trip' package (results in an sp class object
> > (SpatialGridDataFrame)) and this is where I'm having difficulty.  I know
> > maptools allows you to change formats from sp to PBSmapping but I can't
> > seem to identify how to do it for a SpatialGridDataFrame.
> >
> > I get the SpatialGridDataFrame object via:
> >
> > x2009.grid <- makeGridTopology(data2009.sp, cells.dim = c(cell.x1,
> > cell.y1), xlim=xlims, ylim=ylims,buffer = 0, cellsize =
> NULL,adjust2longlat
> > = FALSE)
> > x2009.final <- tripGrid(data2009.sp, grid = x2009.grid, method =
> > "pixellate")
> >
> > For most of these maps I usually just add the grid layer using the image
> > function but what I currently have worked out is quite messy and I think
> > prone to error for other applications.
> >
> > Of course, I can plot the SpatialGridDataFrame object
> > via: spplot(x2009.final) which would be great but I can't figure out how
> to
> > add my coastline via the PBSmapping plotMap call.
> >
> > Could someone please suggest a more direct approach?
> > Thank you.
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
>
>
> --
> Michael Sumner
> Hobart, Australia
> e-mail: mdsumner@gmail.com
>

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