[R-sig-Geo] How to “smooth” a raster map

[Andrew Duff]

You mean re sample?



> On Jun 28, 2015, at 4:25 PM, Thiago V. dos Santos <thi_veloso at yahoo.com.br> wrote:
> 
> Dear all,
> 
> I am trying to create a map from raster data. The file came from a crop model, with resolution of 0.5 degree. Even when I disaggregate it (i.e. increase spatial resolution), the map looks really pixelated. I am trying to make it look better.
> My current code produces this image: http://i.stack.imgur.com/WssPy.png
> 
> where I would like to "smooth" the data, by supressing the pixelated look. Some other visualization programs do this automatically, so I guess it should not be hard to reproduce using R. 
> 
> For example, this is the same file plotted using Panoply: http://i.stack.imgur.com/jXYI7.png
> 
> It doesn't look absolutely smooth, but at least it doesn't have the pixelated look neither. How to achieve a similar result in R? 
> 
> This is the code to reproduce my problem:
> 
> --------------------------------------------------------------------------
> library(RCurl) 
> library(rasterVis)
> 
> # Go to temp dir and download file - approx. 1.7M
> old <- setwd(tempdir())
> 
> # download raster and shapefile
> download.file('https://dl.dropboxusercontent.com/u/27700634/yield.nc', 'yield.nc', method='curl')
> download.file('https://dl.dropboxusercontent.com/u/27700634/southern.zip', 'southern.zip', method='curl')
> unzip('southern.zip', exdir='.')
> 
> # load southern Brazil shapefile
> mapaSHP <- shapefile('southern.shp')
> 
> # load brick
> b <- brick('yield.nc', level=16)
> 
> # create color scheme
> mycols <- rasterTheme(region=colorRampPalette(brewer.pal(9,'Greens'))(100))
> 
> # use second brick layer to plot map
> levelplot(b[[2]], margin = FALSE, main = "Rice yield in tons/ha", par.settings = mycols) +
> layer(sp.lines(mapaSHP, lwd=0.8, col='darkgray'))
> 
> # return to your old dir
> setwd(old)
> 
> --------------------------------------------------------------------------
> Thanks in advance for any input,
> --
> Thiago V. dos Santos
> PhD student
> Land and Atmospheric Science
> University of Minnesota
> http://www.laas.umn.edu/CurrentStudents/MeettheStudents/ThiagodosSantos/index.htm
> Phone: (612) 323 9898
> 
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