[R-sig-Geo] suggestion for sp.grid()

[Dylan Beaudette]

Shouldn't be posting questions late into the night. I realized that my
example was not reproducible.

One more time:

# setup environment
library(gstat)
library(latticeExtra)
library(grid)

# load example data
data(meuse.grid)

coordinates(meuse.grid) <- ~ x + y
gridded(meuse.grid) <- TRUE
meuse.grid$soil <- factor(meuse.grid$soil, labels=c('A','B','C'))


# hacked version of sp.grid()
sp.grid <- function (obj, col = 1, alpha = 1, ...)
{
    if (is.character(obj))
        obj = get(obj)
    xy = coordinates(obj)
    if (length(col) != 1 && length(col) != nrow(xy)) {
    }
    gt = as(getGridTopology(obj), "data.frame")
    grid.rect(x = xy[, 1], y = xy[, 2], width = gt$cellsize[1],
        height = gt$cellsize[2], default.units = "native", gp =
gpar(fill = col, col = NA, alpha = alpha))
}


trellis.par.set(regions=custom.theme()$regions,
superpose.polygon=list(col='black', alpha=0.25))

# first grid covers entire extent
p3 <- spplot(meuse.grid, 'dist', colorkey=list(space='bottom',
width=1, height=0.5, tick.number=3))

# overlay partially transparent, kind of a hack...
p3 <- p3 + layer(sp.grid(meuse.grid[meuse.grid$soil == 'A', ],
col='black', alpha=0.25))

p3 <- update(p3, key=simpleKey('Shaded Region', points=FALSE,
lines=FALSE, rect=TRUE, columns=1, space='top'))

p3




On Tue, Dec 14, 2010 at 11:32 PM, Dylan Beaudette
<dylan.beaudette at gmail.com> wrote:
> Hi,
>
> I was tinkering around with some of the new functions from the
> latticeExtra package, and thought of a (messy) hack for plotting
> multiple grids. However, due to the way sp.grid() is currently coded,
> there is no way to define both grid fill color _and_ outline color:
>
> gp = gpar(fill = col, col = NULL, alpha = alpha)
>
> if this line is changed to...
>
> gp = gpar(fill = col, col = NA, alpha = alpha)
>
> then outlines will default to no color... It might be nice to add a
> new parameter to sp.grid() to allow the user to set the outline color
> of the rectangles produced by grid.rect(). If the above line is
> changed so that col=NA, then it is possible to overlay two grids (kind
> of) like this:
>
>
> library(gstat)
> library(latticeExtra)
> library(grid)
>
> # load example data
> data(meuse.grid)
> coordinates(meuse.grid) <- ~ x + y
> gridded(meuse.grid) <- TRUE
>
> # hacked version of sp.grid()
> sp.grid <- function (obj, col = 1, alpha = 1, ...)
> {
>    if (is.character(obj))
>        obj = get(obj)
>    xy = coordinates(obj)
>    if (length(col) != 1 && length(col) != nrow(xy)) {
>    }
>    gt = as(getGridTopology(obj), "data.frame")
>    grid.rect(x = xy[, 1], y = xy[, 2], width = gt$cellsize[1],
>        height = gt$cellsize[2], default.units = "native", gp =
> gpar(fill = col, col = NA, alpha = alpha))
> }
>
>
> # nice colors
> trellis.par.set(regions=custom.theme()$regions,
> superpose.polygon=list(col='black', alpha=0.25))
>
> # first grid covers entire extent
> p3 <- spplot(meuse.grid, 'dist', colorkey=list(space='bottom',
> width=1, height=0.5, tick.number=3)
>
> # overlay partially transparent, kind of a hack...
> p3 <- p3 + layer(sp.grid(meuse.grid[meuse.grid$soil == 'A', ],
> col='black', alpha=0.25))
>
> # add a new key
> p3 <- update(p3, key=simpleKey('Bad Stuff', points=FALSE, lines=FALSE,
> rect=TRUE, columns=1, space='top'))
>
> print(p3)
>
> Note that I am using an older version of gstat, version 0.9-63. Maybe
> this code has been updated since then. If not, what do you think? Are
> there any better ways to overlay a couple grids?
>
> Cheers,
> Dylan
>