<div>I Glynn,</div>
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<div>Thanks for the reply. I was thinking (and must confess, I was wishing) that with r.mask those pixels that are outside of the mask (i.e. is NULL) can by skiped during the processing.</div>
<div>Anyway, pretty thanks.</div>
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<div>milton<br><br></div>
<div class="gmail_quote">2009/7/7 Glynn Clements <span dir="ltr"><<a href="mailto:glynn@gclements.plus.com">glynn@gclements.plus.com</a>></span><br>
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<div class="h5"><br>Milton Cezar Ribeiro wrote:<br><br>> Just suppose I have a very large - and irregular - region, and that<br>> I am running r.neighbors to compute some moving windows stats. As my<br>> region is irregular, many of central pixels will be NULL. If I use<br>
> r.mask, it means that when I run r.neighbours the processing will be<br>> faster than when I not set r.mask (supposing that the north, south,<br>> west and east will be the same on both case)?<br><br></div></div>
There's no point in using r.mask to mask out pixels which are already<br>null. The mask simply forces specific pixels to be read as null; to<br>the module, such nulls are indistinguishable from nulls in the<br>original data.<br>
<font color="#888888"><br>--<br>Glynn Clements <<a href="mailto:glynn@gclements.plus.com">glynn@gclements.plus.com</a>><br></font></blockquote></div><br>