[GRASS-user] Null or 0?
pertusus at free.fr
Sun Feb 5 04:32:32 EST 2012
On Sun, Feb 05, 2012 at 07:22:29AM -0200, Daniel Victoria wrote:
> Hi Andre,
> On raster algebra, operations using null will return null while operations
> with 0 behaves like expected. Ex:
> 12 x null = null
> 12 x 0 = 0
Also means do not behave the same on NULL, for example when using r.univar
(according to my understanding of the documentation, haven't tested)
NULL cells are excluded from the computation, so 1 cell with a value 1
and 9 NULL will give a mean of 1 while 1 cell with a value 1 and 9 with
value 0 will give a mean of 0.1.
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