[GRASS-user] Exporting set of raster cells with different values as one layer

[Kalindu Perera]

Thanks a lot Moritz..!!!!!!!

I got it and I'll read the mapcalc manual as well.

Thanks again
Best regards
Kalindu Perera

On Fri, 26 Oct 2018 at 13:25, Moritz Lennert <mlennert at club.worldonline.be>
wrote:

>
>
> Am 26. Oktober 2018 09:08:11 MESZ schrieb Kalindu Perera <
> kkc199408 at gmail.com>:
> >Thanks a lot Moritz....!!!!!!!!
> >
> >Can you just send me one example command?..I'm not sure I understood it
> >in
> >the way that you explained
>
> Please do read the r.mapcalc manual, but here's an example:
>
> r.mapcalc "category_range = if(spread_time_observed >= 1 &&
> spread_time_observed <= 90
>  , 1,  null())"
>
> If there are no values below 1 in spread_time_observed, then this can be
> simplified to
>
> r.mapcalc "category_range = if(spread_time_observed <= 90
>  , 1,  null())"
>
> The result of each command is a map with pixel values of 1 where the
> condition is met and null where not.
>
> Moritz
>
> >
> >Thanks again for the quick reply
> >Best regards
> >Kalindu Perera
> >
> >On Fri, 26 Oct 2018 at 11:46, Moritz Lennert
> ><mlennert at club.worldonline.be>
> >wrote:
> >
> >>
> >>
> >> Am 26. Oktober 2018 06:42:44 MESZ schrieb Kalindu Perera <
> >> kkc199408 at gmail.com>:
> >> >Dear all,
> >> >
> >> >I'm doing wildfire simulations in the Grass. I need to calculate the
> >> >area
> >> >of only the wildfire spread from the simulation. For that, I need to
> >> >take
> >> >only the wildfire spread as a separate layer. But the drawback is
> >the
> >> >values of the cells in the spread is different from point to point.
> >But
> >> >it
> >> >has a range. As an example, the values of cells inside the spread
> >are
> >> >ranging from 1-90. The other cells in the map show values more than
> >> >that.
> >> >Can I write a mapcalc command for a range like this to output these
> >> >cells
> >> >as one layer?
> >> >
> >> >@Nikos has sent me this mapcalc command and from that, we can take
> >only
> >> >cells with one value as a layer.
> >> >
> >> >r.mapcalc "category_3 = if(spread_time_observed == 3, 3, null())"
> >> >
> >> >instead of that one value(3) in this can we input a range as
> >> >above(1-90)
> >> >and get all those cells with different values as one layer?
> >>
> >> You can use >/< and the && (logical AND) to select all pixels within
> >a
> >> range in r.mapcalc.
> >>
> >> But you could also use r.reclass or r.recode.
> >>
> >> Moritz
> >>
>
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