Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111
> -----Original Message-----
> From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-
> project.org] On Behalf Of Chris Fowler
> Sent: Monday, November 28, 2011 5:55 PM
> To: r-sig-geo at r-project.org
> Subject: [R-sig-Geo] Overlaying rasters in spplot
>
> I am still having trouble with some raster overlays.
> My trouble now is a result of my not really understanding how layers
> and sp.layout work in the spplot function
>
> I go through a whole mess of steps to get two rasters of identical
> extent and dimension (One is a google map tile, the other my own data)
> Plotting them using the default plot() method within raster, however
> doesn't allow me to have the color palette and breaks I want, so at
> the suggestion of one of the threads on this list I have converted my
> raster objects to SpatialGridDataFrame objects.
>
> I can plot these objects and get exactly what I want using the
> following code:
> layer1<-
> spplot(raster1,"values",at=brks1,col.regions=pal1,colorkey=FALSE)
> layer1
> layer2<-spplot(raster2, "values", at=brks2,col.regions=pal2)
> layer2
>
> from reading the documentation on spplot() from sp package I should be
> able to use the sp.layout attribute to map the second of these layers
> with a transparency of say .5, but I have not been able to get there.
>
> I am hoping that this is enough of a syntax question that the experts
> here can help without a full worked example--my apologies if this is
> not the case.
>
> Thanks in advance,
>
> Chris
>
> Christopher S. Fowler PhD.
> 206.920.1686
> http://csfowler.com
>
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