Ok, didn't check that before since I didn't have the same problem before. Try exporting with a "crazy value" as NA such as in a 16bit unsigned
r.out.gdal etc nodata=65535 Then on R use the mask function such as: mask(x, mask, filename="", inverse=FALSE, maskvalue=65535, updatevalue='NA', ...) might work but its very, you know, hurtful to see :P but I'm like you, I prefer .tif. On 4 September 2014 14:47, Johannes Radinger <johannesradin...@gmail.com> wrote: > > > > On Thu, Sep 4, 2014 at 3:38 PM, Nuno Sá <nunocesard...@gmail.com> wrote: > >> Hello! >> >> Did you try this one? >> >> *r.out.gdal etc nodata*=*'NA'* >> > > As mentioned in the manual of r.out.gdal, the no data parameter takes only > float values > and no strings like 'NA'. Without stating as specific value in GRASS, this > nodata-value is > automatically set to e.g. 65535 for DCELL rasters if I remember correctly > and to 255 > for BYTE rasters. However, this seems not to be recognized when imported > into R with > the package 'raster'. > > /Johannes > > >> >> >> >> On 4 September 2014 14:27, Johannes Radinger <johannesradin...@gmail.com> >> wrote: >> >>> Hi all, >>> >>> of course it is possible to load the raster maps directly via spgrass6. >>> However, we use this work >>> flow also to exchange some of the maps between different users (e.g. via >>> email) and to permanently >>> store single files (geotiffs that contain the proj information within >>> the file). So, I agree that using spgrass6 would be much more efficient, >>> but I'll stick to exporting to geotiffs and so I need to solve the issues >>> with NA's. >>> >>> /Johannes >>> >>> >>> On Thu, Sep 4, 2014 at 2:31 PM, Thomas Adams <tea...@gmail.com> wrote: >>> >>>> Johannes, >>>> >>>> If you want to read your file into R, there is no need to export your >>>> map from GRASS to do this. Simply install and use the R contributed package >>>> 'spgrass6' (spgrass6 has R dependencies that need to be installed first); >>>> it works wonderfully: >>>> >>>> Within GRASS, at the GRASS terminal prompt... >>>> >>>> > library(spgrass6) >>>> Loading required package: sp >>>> Loading required package: XML >>>> GRASS GIS interface loaded with GRASS version: GRASS 7.0.0beta3 (2014) >>>> and location: ohrfc_mpe >>>> > dat<-readRAST6("xmrg0101200306z") >>>> > image(dat) >>>> >>>> This is far more efficient. >>>> >>>> Tom >>>> >>>> >>>> On Thu, Sep 4, 2014 at 5:32 AM, Johannes Radinger < >>>> johannesradin...@gmail.com> wrote: >>>> >>>>> Hi, >>>>> >>>>> I want to export a raster map (FCELL) from GRASS70 to the geotiff >>>>> format using r.out.gdal and to import it later on in R. The map contains >>>>> many no data values. >>>>> >>>>> Here some details about the raster: >>>>> Type of Map: raster Number of Categories: 0 >>>>> Data Type: FCELL >>>>> Rows: 750 >>>>> Columns: 750 >>>>> Total Cells: 562500 >>>>> total null and non-null cells: 15105636 >>>>> total null cells: 15105047 >>>>> >>>>> So when I export the map, r.out.gdal reports: "Input raster map >>>>> contains cells with NULL-value (no-data). The value -nan will be used to >>>>> represent no-data values in the input map. You can specify a nodata value >>>>> with the nodata option." >>>>> >>>>> When I subsequently try to import the geotiff into R (using the >>>>> package 'Raster') the nodata values are not recognised as NA's: >>>>> >>>>> a <- raster("*.tif") >>>>> summary(a) >>>>> Min. 0.5294496 >>>>> 1st Qu. 0.7171210 >>>>> Median 0.7871540 >>>>> 3rd Qu. 1.1581826 >>>>> Max. 1.5494517 >>>>> NA's 0.0000000 >>>>> >>>>> So I am wondering if I need to set any specific parameter during the >>>>> export (r.out.gdal) or import (raster()). >>>>> >>>>> As I am not only exporting FCELL (Float32) raster but also multiple >>>>> (N=500) other rasters to R I would be interested in a solution also for >>>>> DCELL (Float64). Of course I can export all of as Float64 as the file size >>>>> should not be a problem. >>>>> >>>>> Any suggestions or experiences of handling NA's during raster exchange >>>>> between GRASS and R? >>>>> >>>>> /Johannes >>>>> >>>>> _______________________________________________ >>>>> grass-user mailing list >>>>> grass-user@lists.osgeo.org >>>>> http://lists.osgeo.org/mailman/listinfo/grass-user >>>>> >>>> >>>> >>>> >>>> >>> >>> _______________________________________________ >>> grass-user mailing list >>> grass-user@lists.osgeo.org >>> http://lists.osgeo.org/mailman/listinfo/grass-user >>> >> >> >> >> -- >> >> Nuno César de Sá >> +351 91 961 90 37 >> >> > -- Nuno César de Sá +351 91 961 90 37
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