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<body class='hmmessage'><div dir='ltr'>Bernd and Matt: thank you very much for answering.<br>still the ideas are quite confused but your help gave a chance for understanding ;)<br><br>any further suggestion from other users is well accepted!<br><br>all the best,<br>Nic<br><br><br><br><br><br><div><hr id="stopSpelling">Date: Wed, 15 Oct 2014 12:24:09 +1100<br>Subject: Re: [Qgis-user] NoData<br>From: mattslists@gmail.com<br>To: bernd.vogelgesang@gmx.de<br>CC: qgis-user@lists.osgeo.org; sciurusurbanus@hotmail.it<br><br><div dir="ltr">I can contribute a couple of things from my experience with some of these.<div>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.</div><div>I've only come across Nan in tiffs when there's somethings wrong with the format / import.</div><div>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.</div><div><br></div><div>Matt<br></div><div><br></div><div><br></div></div><div class="ecxgmail_extra"><br><div class="ecxgmail_quote">On Wed, Oct 15, 2014 at 10:39 AM, Bernd Vogelgesang <span dir="ltr"><<a href="mailto:bernd.vogelgesang@gmx.de" target="_blank">bernd.vogelgesang@gmx.de</a>></span> wrote:<br><blockquote class="ecxgmail_quote" style="border-left:1px #ccc solid;padding-left:1ex;"><u></u>
<div><div>This post seemes to have drowned, so I dare to bump it, hoping that some less confused people like me might anwser to it.</div><div>I'm using QGIS for years now, but I never figured out how that stuff is supposed to work.</div><div>One of the reasons why I try to do a lot of stuff now in R is that NA is NA !</div><div><br></div><div>Am 08.10.2014, 11:27 Uhr, schrieb Niccolò Marchi <<a href="mailto:sciurusurbanus@hotmail.it" target="_blank">sciurusurbanus@hotmail.it</a>>:<br></div><div><div class="h5"><br><blockquote style="border-left:#0000ff 2px solid;padding-left:1ex;"><div dir="ltr">hi all!<br>please, is there someone who could explain properly all the "NoData topic"?<br><br>I mean:<br>1. differences in setting negative values (-999, -9999, -3.40282e +35, etc) VS NoData (Nan, NoData, NULL)<br>2. how QGIS handles it<br>3. "best practices" or good hints for managing them<br><br>sorry but I've quite a big confusion.<br><br>Thank you very much in advance!<br><br>Nic<br> </div></blockquote><br><br><br></div></div><div><div>-- </div><div>Bernd Vogelgesang<br>Siedlerstraße 2<br>91083 Baiersdorf/Igelsdorf<br>Tel: 09133-825374</div></div></div><br>_______________________________________________<br>
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