Argh! The NULL's were biting me ;-) Did this; [EMAIL PROTECTED] = if(isnull([EMAIL PROTECTED]), 0, 1)
And lo and behold this did work; R_test14 = if([EMAIL PROTECTED], 7, [EMAIL PROTECTED]) And produced the wanted map! But could someone enlighten me as to what exactly is the reason why this worked? regards larsf Søndag 21. september 2008 skreiv Lars Forseth: > Hi! > I wonder if anyone could explain to me how to create a new map (raster) > from two pre-existing maps, in mapcalc. Because I have problems with > understanding how to do this in r.mapcalc > > I have two raster datasets that I would like to combine like so; if the > cell is in map a, assign the value 7; if it is in map B, assign the correct > value from B, (i.e keep the value the cell already have in B). > > I have tried to read "Performing Map Calculations on GRASS Data: r.mapcalc > Program Tutorial", by Marji Larson, Michael Shapiro and Scott Tweddale, > U.S. Army Construction Engineering Research Laboratory (December 1991) , > and they give this example: > > MAPCALC> aspect.str = if(streams,26,aspect) > > This should then give a new map that contains the values from "aspect", but > with the value 26 assigned to cells with "streams". > > Example from my experiments: > R_test9 = if([EMAIL PROTECTED] == 1,7, [EMAIL PROTECTED] ) > > This makes a new map; but it contains only 7, were there was data in > R_vannA, and else, NULL (I guess), see otput below of r.info. > > I also tried "R_test9 = if(if([EMAIL PROTECTED] == 1),7, [EMAIL PROTECTED] ) ; > and this gives the same (non) result. And "R_test10 = if([EMAIL PROTECTED], 7, > [EMAIL PROTECTED])"; also the same as; I.E not what I wanted. The problem is > that it never assigns a value from [EMAIL PROTECTED] > > What am I missing? Or doing wrong? > > Regards > Larsf > > > Running; SUSE 10.3, grass63 dated 12.09 from > http://download.opensuse.org/repositories/Application:/Geo/openSUSE_10.3/i5 >86/ > > > ---------------------------------------------r.info output (example) > > > (3) r.info [EMAIL PROTECTED] > > > > +------------------------------------------------------------------------ > >-- --+ > > > > | Layer: [EMAIL PROTECTED] Date: Sun Sep 21 15:28:36 > > | 2008 > > | > > | | Mapset: larsf Login of Creator: larsf > > | | > > | | Location: Frosta > > | | > > | | DataBase: /home/larsf/grassgis > > | | > > | | Title: ( R_test9 ) > > | | > > | | Timestamp: none > > | > > | ---------------------------------------------------------------------- > > |-- ----| > > | > > | Type of Map: raster Number of Categories: 7 > > | > > | | Data Type: CELL > > | | > > | | Rows: 3360 > > | | > > | | Columns: 3720 > > | | > > | | Total Cells: 12499200 > > | | > > | | Projection: UTM (zone 32) > > | | > > | | N: 7062800 S: 7046000 Res: 5 > > | | > > | | E: 596600 W: 578000 Res: 5 | > > | > > | Range of data: min = 7 max = 7 > > | > > | Data Description: > > | | generated by r.mapcalc > > | > > | Comments: > > | | if([EMAIL PROTECTED] == 1, 7, [EMAIL PROTECTED]) > > > > +------------------------------------------------------------------------ > >-- --+ > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
