[Qgis-user] Raster calculator question

[kimaidou]

Hi Andreas,

I totally agree with the benefit of using SQL-like syntax as in expressions
to calculate rasters.

I would prefer something like
CASE
WHEN raster1 at 1 > raster2 at 1 THEN raster1 at 1
ELSE raster2 at 1
END

Having to multiply the result of a condition (0 or 1) by the band value to
actually get the band values seems cumbersome for some users.
Thanks for raising this issue.

Michael


2014-04-24 15:25 GMT+02:00 Andreas Neumann <a.neumann at carto.net>:

> Hi Carlos,
>
> Thanks a lot. This works fine.
>
> Seems I first have to get used to the raster calculator syntax. Would be
> great if it would use the expression editor as is used almost everywhere
> else.
>
> Andreas
>
> Am 24.04.2014 12:57, schrieb Carlos Cerdán:
> > Hi Andreas:
> >
> > Yes, it always evaluates to true because of "OR" condition , so try:
> >
> > (lake_mask > 0) * lake_mask + (lake_mask<=0)*dtm
> >
> > Good luck
> >
> > Carlos
> >
> >
> >
> >
> > 2014-04-24 1:53 GMT-05:00 Andreas Neumann <a.neumann at carto.net>:
> >
> >> Hi,
> >>
> >> I have a hard time understanding the raster calculator syntax.
> >>
> >> I would like to merge two rasters: DTM and lake mask. Let's call the one
> >> dtm and the other lake_mask.
> >>
> >> When the lake_mask has a value > 0 then I would like to take the value
> >> of the lake_mask, otherwise the value of the dtm.
> >>
> >> What would an appropriate syntax look like?
> >>
> >> I tried something along
> >>
> >> ((lake_mask > 0) * lake_mask) OR dtm
> >>
> >> But all I get in the resulting grid are values of 1. I guess it is
> >> because it always evaluates to true?
> >>
> >> Thanks for your help.
> >>
> >> Andreas
> >> _______________________________________________
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> >>
> >
> >
> >
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