[R-sig-Geo] Plotting polygons on top of a levelplot

[Ryan Anderson]

That likely gives me the control over the color ramp that I am looking
for, but I still have trouble plotting the vector layer over the top of
the resulting image plot.
If I do:
 spplot(spdf["dist"],col.regions=heat.colors(400), at = 0:10/10)
 plot(river, add = TRUE)
I still get the plot.new has not been called yet error after I attempt to
add the river data.  What am I doing wrong?

Thanks,
Ryan


> Ryan, you're probably looking for something like
>
> spplot(spdf["dist"],col.regions=heat.colors(400), at = 0:10/10)
>
> spplot is a wrapper around lattice functions for spatial data, and tries
> to pass on all the lattice controls.
> --
> Edzer
>
> Ryan Anderson wrote:
>> I have some gridded spatial data that I want to plot with a vector
>> overlay
>> on top.  The following reproducible code makes a figure similar to the
>> one
>> I am ultimately trying to produce:
>>
>> library(sp)
>> library(fields)
>> data(meuse.grid)
>> data(meuse.riv)
>> coords <- SpatialPixels(SpatialPoints(meuse.grid[, c("x","y")]))
>> spdf <- SpatialPixelsDataFrame(coords, meuse.grid)
>> fullgrid(spdf)<-TRUE
>> river<-SpatialPolygons(list(Polygons(list(Polygon(meuse.riv)),"meuse.riv")))
>> par(mar = c(5,5,5,8), col.axis = 1)
>> ramp = heat.colors(400)
>> image(spdf, "dist", axes = TRUE, col = ramp)
>> plot(river, add = TRUE)
>> zvals<-spdf$dist
>> zvals<-zvals[!is.na(zvals)]
>> image.plot(zlim = c(min(zvals), max(zvals)), nlevel = 256, legend.only =
>> TRUE, col = ramp)
>>
>> I need more control over the legend and the color ramp than I know how
>> to
>> achieve with this code.  I can create the plot I want with levelplot by
>> setting the 'at' component 'colorkey', but when I try to overlay the
>> vector file I get an error.  Here is a simplified version of the code I
>> tried:
>>
>> #try a levelplot
>> library(lattice)
>> x11()
>> par(mar = c(5,5,5,8))
>> x<-spdf$x
>> y<-spdf$y
>> z<-spdf$dist
>> levelplot(z~x+y)
>> plot(river, add = TRUE)
>> #Gives Error in polygon(x = x, y = y, border = border, col = col, lty =
>> #lty,  :
>> #  plot.new has not been called yet
>>
>> I need to either find a way to control the mapping of data values to the
>> color ramp more precisely in my call to image or image.plot or to find a
>> way to plot a ploygon over the top of a levelplot.
>>
>> My color ramp goals more specifically: my grid contains both positive
>> and
>> negative values, and they are not necessarily symmetrically distributed
>> around zero.  I want to plot them so that zero is white, negative values
>> are symbolized with a ramp from white to blue (with darker shades for
>> lower values) and positive values are symbolized with a ramp from white
>> to
>> red (with darker shades for higher values).
>>
>> Thanks for your help!
>>
>> _______________________________________________
>> R-sig-Geo mailing list
>> R-sig-Geo at stat.math.ethz.ch
>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>
> --
> Edzer Pebesma
> Institute for Geoinformatics (ifgi), University of Münster,
> Weseler Straße 253, 48151 Münster, Germany.  Phone: +49 251
> 8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de/
>
>