[GRASS-user] saving patch areas on raster maps

GRASS GRASS user
1

Dear all,

I generated a clump map from my cover map, and computed the area of each patch using r.stats.
Now I need generate a map which values is the area for each clump.

Suggestions are welcome.

Best regards,

miltinho astronatua
brazil

2

You can use r.recode to do this, but you’ll need to reformat the output from r.stats.

Example:

r.stats -a -n

0 1234
1 2345
2 3456
…

This needs to be:

0:0:1234:1234
1:1:2345:2345
2:2:3456:3456
…

Save this to a txt file and use it with the rules flag of r.recode. If you have a large amount of categories, I would suggest using awk or perl to reformat the r.stats output.

-Jamie

On Fri, Nov 14, 2008 at 8:22 AM, Milton Cezar Ribeiro <miltinho.astronauta@gmail.com> wrote:

Dear all,

I generated a clump map from my cover map, and computed the area of each patch using r.stats.
Now I need generate a map which values is the area for each clump.

Suggestions are welcome.

Best regards,

miltinho astronatua
brazil

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3

Milton wrote:

> I generated a clump map from my cover map, and computed the area of each
> patch using r.stats.
> Now I need generate a map which values is the area for each clump.

Jamie Adams wrote:

You can use r.recode to do this, but you'll need to
reformat the output from r.stats.

another way is set areas as r.category labels, then create a new map
from the labels using r.mapcalc's @ operator. Again, perhaps some
reformatting is needed with awk etc. to rearrange column order?

Hamish

4

Dear all,

Thanks for all tips.
The code below worked fine. As my map is in meters, I saved the wanted AREA OF CLUMPs in hectare.

r.stats -na input=clump_map | awk ‘{print $1,“=”,$2/10000}’|r.reclass input=clump_map output=clump_map_AreaHA -

All the best, for all.

miltinho
brazil

2008/11/16 Hamish <hamish_b@yahoo.com>

Milton wrote:

I generated a clump map from my cover map, and computed the area of each
patch using r.stats.
Now I need generate a map which values is the area for each clump.

Jamie Adams wrote:

You can use r.recode to do this, but you’ll need to
reformat the output from r.stats.

another way is set areas as r.category labels, then create a new map
from the labels using r.mapcalc’s @ operator. Again, perhaps some
reformatting is needed with awk etc. to rearrange column order?

Hamish