Try fasterize, converting to spatstat from raster is straightforward, happy to help.
https://github.com/ecohealthalliance/fasterize Cheers, Mije On Fri, 2 Jun 2017, 07:45 Rolf Turner, <r.tur...@auckland.ac.nz> wrote: > > On 02/06/17 01:17, lluis.hurt...@uv.es wrote: > > > Dear all, > > > > I am currently working with the spatstat package, using windows and > pixel images. > > > > First: > > > > My aim is to transform a shapefile (see attached) into a pixel image. > > > > My idea is to start transforming the shapefile into a Spatial Polygon > file: > > > > x <- readShapeSpatial("200001441.shp") > > y <- as(x, "SpatialPolygons") > > z <- as.owin(y) > > > > Given z, I want to identify each polygon with a single constant value. > This is like adding marks to the SpatialPolygons file. Then I want to > convert these polygons into an image, such that the value of each pixel > corresponds to the value associated to the polygon where the pixel lies. > > > > I have been able to do this individually, polygon by polygon, but then I > cannot merge the resulting images into a single one. Any idea? > > > > Second: > > > > I would also need a single window containing all the smallest polygons > (the boundary). I have tried: > > > > w <- union.owin(z) > > > > But the resulting window w still shows internal polygons. As read in > spatstas FAQ page: > > > > "First, convert each of the regions into a separate owin object. Then > apply union.owin to combine them." > > > > So I try, > > > > regions <- slot(y, "polygons") > > regions <- lapply(regions, function(x) { SpatialPolygons(list(x)) }) > > windows <- lapply(regions, as.owin) > > > > But windows is a list of 4307 polygons. How can introduce all of them as > a single argument? > > > >> M <- union.owin(windows) > > Warning messages: > > 1: In union.owin(windows) : Some arguments were not windows > > 2: In union.owin(windows) : No windows were given > > > > > > Thank you very much for you help. > > As Don has said, this question would be better asked on R-sig-geo. > > A *reproducible* example would be nice, e.g. perhaps you could tell us > how to get the shapefile in question. > > In respect of your last point: Rather than "M <- union.owin(windows)" > you should use: > > M <- do.call(union.owin, windows) > > But that's rather off the track. What I think you should do (it's hard > to be certain without a reproducible example) is something like: > > tw <- tess(tiles=windows) > iw <- as.im(funxy(as.function(tw,values=vvv),W=Window(tw)),dimyx=128) > > where "vvv" is a vector of the values that you wish to associate with > the individual polygons. There may be less cryptic ways of > accomplishing the same thing, but this is the sexiest way, I think. > > The value chosen for "dimyx", i.e. 128, is just by way of example. You > can use whatever value suits you. The larger it is, the smoother the > individual polygons will look, in pixellated form, but the longer things > will take. With 4307 polygons, that might be a rather long time! > > HTH > > cheers, > > Rolf Turner > > -- > Technical Editor ANZJS > Department of Statistics > University of Auckland > Phone: +64-9-373-7599 ext. 88276 > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Dr. Michael Sumner Software and Database Engineer Australian Antarctic Division 203 Channel Highway Kingston Tasmania 7050 Australia [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
