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 > >
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