#3679: Convert numeric raster category labels to numeric column in the output
vector map's attribute table
-------------------------------+-------------------------
Reporter: Nikos Alexandris | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: minor | Milestone: 7.8.0
Component: Raster | Version: svn-trunk
Resolution: | Keywords: r.to.vect
CPU: Unspecified | Platform: Unspecified
-------------------------------+-------------------------
Comment (by Nikos Alexandris):
An virtual example using maps from the
[https://grass.osgeo.org/sampledata/north_carolina/nc_basic_spm_grass7.tar.gz
nc_basic_spm_grass7.tar.gz] Location:
An integer version of the `elevation` map
{{{
r.info elevation_int -r
min=55
max=156
}}}
and the `geology` map
{{{
r.report geology -hn --q
+-----------------------------------------------------------------------------+
| Category Information
|
| #|description
|
|-----------------------------------------------------------------------------|
|217|CZfg
|
|262|CZlg
|
|270|CZig
|
|405|CZbg
|
|583|CZve
|
|720|CZam
|
|766|CZg
|
|862|CZam
|
|910|CZbg
|
|921|Km
|
|945|CZbg
|
|946|CZam
|
|948|CZam
|
+-----------------------------------------------------------------------------+
}}}
Compute the average elevation value
for each geology "type",
and store it as a category label
in the output raster map `elevation_of_geologies`
{{{
r.stats.zonal -r base=geology cover=elevation method=average
output=elevation_of_geologies
First pass
100%
Generating reclass map
}}}
Report the new map's categories and labels,
in which case, these are
the geology "type"
and the average elevation
{{{
r.report -hn --q elevation_of_geologies
+-----------------------------------------------------------------------------+
| Category Information
|
| #|description
|
|-----------------------------------------------------------------------------|
|217|118.926884
|
|262|108.969823
|
|270|92.227103
|
|405|132.957558
|
|583|139.353428
|
|720|124.298955
|
|766|132.427368
|
|862|118.309800
|
|910|94.204611
|
|921|135.215935
|
|945|127.235592
|
|946|89.908638
|
|948|129.016971
|
+-----------------------------------------------------------------------------+
}}}
Convert the raster map `elevation_of_geologies`
into a vector map named `elevation_of_geologies_vector`,
via
{{{
r.to.vect elevation_of_geologies output=elevation_of_geologies_vector
type=area
Extracting areas...
100%
Writing areas...
100%
Building topology for vector map <elevation_of_geologies_vector@user1>...
Registering primitives...
49 primitives registered
1068 vertices registered
Building areas...
100%
13 areas built
One isle built
Attaching islands...
100%
Attaching centroids...
100%
Number of nodes: 24
Number of primitives: 49
Number of points: 0
Number of lines: 0
Number of boundaries: 36
Number of centroids: 13
Number of areas: 13
Number of isles: 1
r.to.vect complete.
}}}
The new vector map has the following attributes:
{{{
v.info -c elevation_of_geologies_vector
Displaying column types/names for database connection of layer <1>:
INTEGER|cat
INTEGER|value
CHARACTER|label
}}}
It would be a convenience to actually have `r.to.vect` create a column of
type `INTEGER` or `DOUBLE PRECISION` for the "average elevation values",
according to the type of numbers that are stored as raster category
labels.
Something like an `-n` flag (`-n` Write raster category labels as numeric
values), i.e.
{{{
r.to.vect -n elevation_of_geologies output=elevation_of_geologies_vector
type=area
}}}
could produce a vector map for which `v.info -c
elevation_of_geologies_vector` will show something like:
{{{
INTEGER|cat
INTEGER|value
INTEGER|statistics
}}}
or
{{{
INTEGER|cat
INTEGER|value
DOUBLE PRECISION|statistics
}}}
--
Ticket URL: <https://trac.osgeo.org/grass/ticket/3679#comment:2>
GRASS GIS <https://grass.osgeo.org>