[R-sig-Geo] Drawing lines in raster cells

[Lionel]

Yes, this is it, thank you very much for your help.
Lionel

On 13/05/2013 18:42, Robert J. Hijmans wrote:
> Lionel, perhaps this is what you are after. Robert
>
> library(raster)
> library(rgeos)
>
> r <- raster(ncols=10,nrows=10)
> set.seed(0)
> r[] <- sample(0:1,100,replace=TRUE)
>
> p <- rasterToPolygons(r, fun=function(x){x==1}, dissolve=TRUE)
>
> plot(r)
> plot(p, add=T, density=4)
>
>
>
> On Sun, May 12, 2013 at 8:49 AM, Lionel <s6lihert at uni-bonn.de> wrote:
>> Hi Oscar,
>>
>> Thanks for your help, what I would like to get is something similar to this:
>> http://www.google.fr/imgres?q=species+range+shift&start=280&um=1&sa=N&hl=fr&biw=1366&bih=647&tbm=isch&tbnid=MdhZVMKVLMSH3M:&imgrefurl=http://www.scielo.sa.cr/scielo.php%3Fscript%3Dsci_arttext%26pid%3DS0034-77442008000200028&docid=9u3QDKVd0hdQqM&imgurl=http://www.scielo.sa.cr/img/revistas/rbt/v56n2/art28i2.jpg&w=363&h=432&ei=cbiPUe_4BqO80QX-hoCIBw&zoom=1&iact=hc&vpx=588&vpy=170&dur=342&hovh=180&hovw=152&tx=83&ty=124&page=10&tbnh=159&tbnw=134&ndsp=30&ved=1t:429,r:84,s:200,i:256
>>
>> Where each raster cells with a certain values (say 1) get crossed by a
>> diagonal line.
>>
>> Your code is achieving something different, concerning the object created
>> the best would be a Spatial* object, however I think I could be able to find
>> a way around using ggmap.
>>
>> Thanks again,
>> Lionel
>>
>>
>> On 12/05/2013 16:23, Oscar Perpiñán Lamigueiro wrote:
>>>
>>> Hi Lionel,
>>>
>>> With this code you will draw lines connecting raster cells with a
>>> certain value. I am not sure if you also need to build a SpatialLines
>>> object with them (which you won't get with my code):
>>>
>>> library(raster)
>>> library(latticeExtra) ## to use +.trellis and layer()
>>>
>>> r1<-raster(ncols=10,nrows=10)
>>> r1[]<-sample(0:1,100,replace=TRUE)
>>>
>>> ## extract coordinates of those cells with a condition
>>> myCells <- Which(r1==1, cells=TRUE)
>>> xy <- xyFromCell(r1, myCells)
>>>
>>> ## border and border.lwd are only needed to highlight the cells boundaries
>>> spplot(r1, at=c(0, 0.5, 1), border='black', border.lwd=0.3) +
>>>       layer(llines(xy, type='b', col='black'))
>>>
>>>
>>> Best,
>>>
>>> Oscar.
>>>
>>> Lionel <s6lihert at uni-bonn.de> writes:
>>>
>>>> Dear List,
>>>>
>>>> I would like to draw lines in raster cells with a certain values, I can
>>>> work around this with a for loop but as always this solution only works
>>>> for small datasets (which is not my case), I would therefore like to
>>>> have your opinion on this;
>>>>
>>>> #the code
>>>> library(maptools) #to use spRbind
>>>> out<-NULL
>>>> r1<-raster(ncols=10,nrows=10)
>>>> r1[]<-sample(0:1,100,replace=TRUE)
>>>> for(i in 1:ncell(r1)){
>>>>      if(r1[i]==1){
>>>>
>>>> lines<-SpatialLines(list(Lines(list(Line(matrix(c(xyFromCell(r1,i)+(res(r1)/2),xyFromCell(r1,i)-(res(r1)/2)),ncol=2,byrow=TRUE))),ID=as.character(i))))
>>>>        if(is.null(out)){
>>>>          out<-lines }
>>>>           else {out<-spRbind(out,lines)}
>>>>        }
>>>>      print(i)
>>>> }
>>>>
>>>> Thank you in advance,
>>>
>>>
>>>
>>
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