I can contribute a couple of things from my experience with some of these. 1. there are some gotchas with using NULL (in vector files) is that the result of X+NULL or X concatenate NULL, effectively any operation using NULL the result is NULL. This is expected/deliberate. I've only come across Nan in tiffs when there's somethings wrong with the format / import. Nodata seems to be specified, the default is set at 0 on most files/formats I've dealt with (usually single band rasters) and its handled the same way as if I specify -999.
Matt On Wed, Oct 15, 2014 at 10:39 AM, Bernd Vogelgesang < [email protected]> wrote: > This post seemes to have drowned, so I dare to bump it, hoping that some > less confused people like me might anwser to it. > I'm using QGIS for years now, but I never figured out how that stuff is > supposed to work. > One of the reasons why I try to do a lot of stuff now in R is that NA is > NA ! > > Am 08.10.2014, 11:27 Uhr, schrieb Niccolò Marchi < > [email protected]>: > > hi all! > please, is there someone who could explain properly all the "NoData topic"? > > I mean: > 1. differences in setting negative values (-999, -9999, -3.40282e +35, > etc) VS NoData (Nan, NoData, NULL) > 2. how QGIS handles it > 3. "best practices" or good hints for managing them > > sorry but I've quite a big confusion. > > Thank you very much in advance! > > Nic > > > > > -- > Bernd Vogelgesang > Siedlerstraße 2 > 91083 Baiersdorf/Igelsdorf > Tel: 09133-825374 > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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