[R-sig-Geo] fix color scale

[Dylan Beaudette]

Ah,

Thanks for the clarification. I'll review the changelog before giving my 
opinions!

Cheers,
Dylan

On Sunday, November 07, 2010, Edzer Pebesma wrote:
> Dylan, I believe that lattice (grid) recently improved the plotting of
> rasters quite a bit, by using panel.levelplot.raster instead of
> panel.levelplot - some function in grid now renders rasters faster on
> devices for which this is optimed.
> 
> spplot also has to transform the data to long format, by calling
> sp:::spmap.to.lev, which in turn uses a stack method for
> SpatialPointsDataFrame objects; this in turn uses stack.data.frame
> 
> Bests,
> 
> 
> On 11/08/2010 05:00 AM, Dylan Beaudette wrote:
> > Interesting demonstration. However, it seems like sp objects and
> > spplot are still more efficient at storing / plotting large grids. The
> > example listed below required over 2 minutes to complete on a 2.4 Ghz
> > Intel processor. Also, storing the coordinates + data in long format
> > could easily fill available memory with large rasters. I have found
> > that storing multiple raster attributes as columns in the @data slot
> > of a SpatialGridDataFrame object give me flexibility to plot images
> > with a consistent color scheme, without needing to store the data in
> > long format. Also with lattice, the plots are generated in a couple of
> > seconds (500x700 px grid). I would be very interested in knowing how
> > to make ggplot() any faster.
> > 
> > Cheers!
> > Dylan
> > 
> > On Sun, Nov 7, 2010 at 11:55 AM, Edzer Pebesma
> > <edzer.pebesma at uni-muenster.de> wrote:
> >> Paul, this nicely illustrates the power of ggplot2.
> >>
> >> In the resulting plot, however, it seems to me that the
> >>
> >> + opts(aspect.ratio = 1)
> >>
> >> does not result in the desired effect that 1 m in the x direction equals
> >> 1 m in the y direction. Standard plot (asp = 1), and lattice plots (asp
> >> = "iso") have this; what does ggplot2 need?
> >>
> >> On 10/31/2010 11:31 AM, Paul Hiemstra wrote:
> >>> Hi Peter,
> >>>
> >>> When creating such a large amount of illustrations with the same
> >>> colorscale, I automatically think of lattice graphics. Under the hood
> >>> spplot also uses lattice graphics. Take a look at the levelplot()
> >>> function from lattice which produces the grid plots for spplot (if I'm
> >>> correct). Alternatively, I've been using ggplot now for quite a while to
> >>> make plots of a lot of grids. A small example says more than a thousand
> >>> words:
> >>>
> >>> library(ggplot2)
> >>> library(sp)
> >>>
> >>> data(meuse.grid)
> >>> summary(meuse.grid)
> >>>
> >>> # Note that I do not transform meuse.grid to SpatialPixelsDataFrame
> >>> # Let's make a simple grid plot
> >>> dum = meuse.grid[c("x","y","dist")]
> >>> ggplot(aes(x = x, y = y, fill = dist), data = dum) + geom_tile()
> >>>
> >>> # Let's make a few more attributes to the grid
> >>> # could be measurements on other dates for example
> >>> new_atts = do.call("cbind", lapply(1:100, function(num) dum$dist +
> >>> runif(dum$dist)))
> >>> summary(new_atts)
> >>> dum = data.frame(cbind(dum, new_atts))
> >>>
> >>> # Important step now is to
> >>> # restructure the data
> >>> dum_ggplot = melt(dum, id.vars = c("x","y"))
> >>>
> >>> # Now make a plot using dum_ggplot
> >>> # of 'x' and 'y' using value as a 'fill'
> >>> # with a plot per 'variable', can take a minute to plot
> >>> ggplot(aes(x = x, y = y, fill = value), data = dum_ggplot) + geom_tile()
> >>> + facet_wrap(~variable) +
> >>>       scale_x_continuous('', labels = NA, breaks = NA) +
> >>>       scale_y_continuous('', labels = NA, breaks = NA) +
> >>> opts(aspect.ratio = 1)
> >>> # These last two lines get rid of the labels on the axes and set aspect
> >>> ratio to 1
> >>>
> >>> Now you have a plot with 101 maps with the same colorscale, with ggplot
> >>> doing all the hard work. It takes some time to get the hang of ggplot,
> >>> but I think it is worth the investment, also for spatial plots.
> >>>
> >>> cheers and hope this helps,
> >>> Paul
> >>>
> >>> On 10/28/2010 09:12 PM, Peter Larson wrote:
> >>>> Hello!
> >>>>
> >>>> I have a problem.
> >>>>
> >>>> I am using IDW to interpolate a daily series of geospatial
> >>>> observations. Thus, I want to produce a large number of sequential
> >>>> maps.
> >>>>
> >>>> I want them to all represent the same color scale. Is there any way to
> >>>> fix the color scale so that it is the same for all the plots?
> >>>>
> >>>> Thanks,
> >>>>
> >>>> Pete
> >>>>
> >>>> _______________________________________________
> >>>> 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
> >> http://www.52north.org/geostatistics      e.pebesma at wwu.de
> >>
> >> _______________________________________________
> >> 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
> http://www.52north.org/geostatistics      e.pebesma at wwu.de
>