[R-sig-Geo] raster::plot() common color scale?

[Robert J. Hijmans]

> Would this problem be avoided by the new wrapper provided by Robert?

Yes, through its "maxpixels" argument (which has a default value).


On Wed, Jun 15, 2011 at 7:59 AM, Agustin Lobo <alobolistas at gmail.com> wrote:
> Paul,
>
> While this is certainly the most elegant solution, would it work with
> really large raster objects? Note that you
> make a data.frame, and the most important characteristic of package
> raster is its ability to do not incorporate
> the actual raster values to the raster objects to save memory.
>
> Would this problem be avoided by the new wrapper provided by Robert?
>
> Thanks
>
> Agus
>
> 2011/6/10 Paul Hiemstra <paul.hiemstra at knmi.nl>:
>>  Hi,
>>
>> I would recommend using one of the more advanced plotting facilities in
>> R, ggplot. An example:
>>
>> library(ggplot2)
>> library(raster)
>> theme_set(theme_bw())
>>
>> r = raster(system.file("external/test.grd", package="raster"))
>>
>> # Convert to data.frame
>> r_df = as.data.frame(as(r, 'SpatialPixelsDataFrame'))
>> # create new column 10 times larger
>> # here you could extract data from other grids that
>> # you want to show at the same time
>> r_df$valuesx10 = r_df$values*2
>>
>> # Reshape the data for ggplot
>> plotData = melt(r_df, id.vars = c('x','y'))
>>
>> ggplot(aes(x = x, y = y), data = plotData) +
>>    geom_tile(aes(fill = value)) + facet_wrap(~ variable) +
>>    scale_fill_gradient(low = 'white', high = 'blue') +
>>    coord_equal()
>>
>> This is a basic ggplot example of visualizing rasters. I realize that it
>> is a short example with a lot of things specific to ggplot, but I hope
>> you can figure out why I use the code that I use. In my view, the
>> investment in learning to use ggplot is worth it. A good place to start
>> is the ggplot website [1].
>>
>> cheers.
>> Paul
>>
>> [1] http://had.co.nz/ggplot2/
>>
>> On 06/09/2011 01:59 PM, Agustin Lobo wrote:
>>> Hi!
>>> I'm doing
>>>
>>> par(mfrow=c(2,2))
>>> plot(simr)
>>> plot(simrlisa)
>>> a2 = simr>l$lisamax
>>> plot(l$lisamax)
>>> plot(simr*a2)
>>>
>>> where simr, l%lisamax and a2 are raster objects. Is there any way to
>>> get a common color scheme
>>> (i.e., setting common min and max values)?
>>> The color table is the same, but the scaling is independent for each
>>> raster object and cannot be compared.
>>>
>>> Thanks
>>>
>>> Agus
>>>
>>> _______________________________________________
>>> R-sig-Geo mailing list
>>> R-sig-Geo at r-project.org
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>
>>
>> --
>> Paul Hiemstra, Ph.D.
>> Global Climate Division
>> Royal Netherlands Meteorological Institute (KNMI)
>> Wilhelminalaan 10 | 3732 GK | De Bilt | Kamer B 3.39
>> P.O. Box 201 | 3730 AE | De Bilt
>> tel: +31 30 2206 494
>>
>> http://intamap.geo.uu.nl/~paul
>> http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770
>>
>>
>