[tlocoh-info] problem in converting isopleths to rasters
g.cerritelli
giulia.cerritelli at biologia.unipi.it
Tue Apr 20 10:20:14 CEST 2021
Hi all,
I have a question on converting isopleths to rasters using the function
lhs.iso.rast.
My final goal is to evaluate the percentage of overlap between animals
home range for which I would like to use the function kerneloverlap in
adehabitatHR. To this aim I need to convert the isopleths of all animals
using the same raster for all animals as grid. I have tried to use the
function lhs.iso.rast setting in the function arguments a raster layer
as grid, but I get an error I don't know how to solve. I would really
appreciate if anyone can give me some suggestions on how to solve the
problem.
Here I have reported an example:
##Create the locoh-xy and select one ID
utm.lxy <- xyt.lxy(xy = coordinates(data.utm), dt=NULL, id= data.utm$ID,
proj4string=CRS("+proj=utm +zone=32 +ellps=intl +units=m +no_defs"))
lxy_89 <- lxy.subset(utm.lxy, id = "3")
##I use the a-method and select the best values (I have not reported
here all the selection procedures) and then I finally obtain the lhs
object
89.lhs.a <- lhs.select(89.lhs.amixed, a=160000)
##I create a SpatialPixel that I then transform to raster
> x <- seq(519000, 791000, by=500) # resolution is the pixel size you
> desire (500 m)
> y <- seq(4500000, 4900000, by=500)
> xy <- expand.grid(x=x,y=y)
> coordinates(xy) <- ~x+y
> gridded(xy) <- TRUE
> class(xy)
[1] "SpatialPixels"
attr(,"package")
[1] "sp"
> r <- raster(xy)
> proj4string(r) = proj4string(data.utm)
> r
class : RasterLayer
dimensions : 801, 545, 436545 (nrow, ncol, ncell)
resolution : 500, 500 (x, y)
extent : 518750, 791250, 4499750, 4900250 (xmin, xmax, ymin, ymax)
crs : +proj=utm +zone=32 +ellps=intl +units=m +no_defs
##I try to convert the isopleths to raster, and here I get the error
> SCOLA_89.lhs.a <- lhs.iso.rast(SCOLA_89.lhs.a, raster = r, status=TRUE)
Converting isopleths to rasters
3.pts812.a160000.s0.kmin0
Error in round(nrows) : non-numeric argument to mathematical function
##Note: If I use just the cell size as argument, the function correctly
transforms the isopleths, thus I don't think it is a problem in the lhs
object
> SCOLA_89.lhs.a <- lhs.iso.rast(SCOLA_89.lhs.a, cell.size=100,
> status=TRUE)
Converting isopleths to rasters
3.pts812.a160000.s0.kmin0
|=================================================================================|
100%
Total time: 3.4 secs
Thank you in advance for any help you can provide
Best,
Giulia
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