[GRASS-SVN] r58539 - grass/trunk/vector/v.extract
svn_grass at osgeo.org
svn_grass at osgeo.org
Fri Dec 27 08:53:51 PST 2013
Author: neteler
Date: 2013-12-27 08:53:51 -0800 (Fri, 27 Dec 2013)
New Revision: 58539
Modified:
grass/trunk/vector/v.extract/v.extract.html
Log:
Milena Nowotarska: update examples to NC dataset
Modified: grass/trunk/vector/v.extract/v.extract.html
===================================================================
--- grass/trunk/vector/v.extract/v.extract.html 2013-12-27 16:50:39 UTC (rev 58538)
+++ grass/trunk/vector/v.extract/v.extract.html 2013-12-27 16:53:51 UTC (rev 58539)
@@ -7,7 +7,8 @@
Dissolving (optional) is based on the output categories. If 2 adjacent
areas have the same output category, the boundary is removed.
-<p>If <b>cats</b>, <b>file</b>, <b>random</b> or <b>where</b> options are not
+<p>
+If <b>cats</b>, <b>file</b>, <b>random</b> or <b>where</b> options are not
specified, all features of given type and layer are
extracted. Categories are not changed in that case.
@@ -20,27 +21,31 @@
<h2>EXAMPLES</h2>
+The examples are intended for the North Carolina sample dataset:
+
<h3>Extract areas by category number with dissolving #1:</h3>
<div class="code"><pre>
-v.extract -d cats=1,2,3,4 input=soils output=soil_groupa type=area new=0
+v.extract -d cats=1,2,3,4 input=soils_wake output=soil_groupa type=area new=0
</pre></div>
-<p>produces a new vector <b>soil_groupa</b>, containing those areas from vector
+<p>
+produces a new vector <b>soil_groupa</b>, containing those areas from vector
<b>soils</b> which have category numbers <b>1 thru 4</b>; any common boundaries are
dissolved, and all areas in the new map will be assigned category number 0.
<h3>Extract areas by category number with dissolving #2:</h3>
<div class="code"><pre>
-v.extract -d cats=1-4 input=soils output=soil_groupa type=area new=-1
+v.extract -d cats=1-4 input=soils_wake output=soil_groupa type=area new=-1
</pre></div>
-<p>produces a new vector map <b>soil_groupa</b> containing the areas from vector
+<p>
+produces a new vector map <b>soil_groupa</b> containing the areas from vector
<b>soils</b> which have categories <b>1 thru 4</b>. Any common boundaries are
dissolved, all areas in the new map will retain their original category
numbers 1 thru 4, since <b>new</b> was set to -1.
<h3>Extract all areas and assign the same category to all:</h3>
<div class="code"><pre>
-v.extract input=soils output=soil_groupa type=area new=1
+v.extract input=soils_wake output=soil_groupa type=area new=1
</pre></div>
<p>
produces a new vector map <b>soil_groupa</b> containing all areas from
@@ -49,7 +54,8 @@
<h3>Extract vectors with SQL:</h3>
<div class="code"><pre>
-v.extract input=markveggy.shp output=markveggy.1 new=13 where="(VEGTYPE = 'Wi') or (VEGTYPE = 'PS') or (PRIME_TYPE='Wi')"
+v.extract input=markveggy.shp output=markveggy.1 new=13 \
+ where="(VEGTYPE = 'Wi') or (VEGTYPE = 'PS') or (PRIME_TYPE='Wi')"
</pre></div>
<p>
produces a new vector map with category number 13 if the SQL statement is
@@ -57,59 +63,62 @@
<h3>Extract vector features which have the given field empty:</h3>
<div class="code"><pre>
-v.extract input=forest output=forest_gaps where="CANOPY is NULL"
+v.extract input=lakes output=lakes_gaps where="FTYPE is NULL"
</pre></div>
<h3>Extract vector features which have the given field not empty:</h3>
<div class="code"><pre>
-v.extract input=forest output=forest_canopy where="CANOPY not NULL"
+v.extract input=lakes output=lakes_ftype where="FTYPE not NULL"
</pre></div>
<h3>Reverse extracting (behaves like selective vector objects deleting):</h3>
-Remove unreferenced stations from the GlobalSOD database:
+Remove meteorological stations from map which are located above 1000m:
<div class="code"><pre>
# check what to delete:
-v.db.select gsod_stationlist where="latitude < -91"
+v.db.select precip_30ynormals where="elev > 1000"
# perform reverse selection
-v.extract -r gsod_stationlist out=gsod_stationlist_clean where="latitude < -91"
+v.extract -r input=precip_30ynormals output=precip_30ynormals_lowland \
+ where="elev > 1000"
-v.db.select gsod_stationlist_clean
+# verify
+v.db.select precip_30ynormals_lowland
</pre></div>
<h3>Dissolving based on column attributes:</h3>
<div class="code"><pre>
# check column names:
-v.info -c polbnda_italy
+v.info -c zipcodes_wake
# reclass based on desired column:
-v.reclass polbnda_italy out=polbnda_italy_recl_nam col=vmap_nam
+v.reclass input=zipcodes_wake output=zipcodes_wake_recl_nam column=ZIPNAME
# verify:
-v.info -c polbnda_italy_recl_nam
-v.db.select polbnda_italy_recl_nam
+v.info -c zipcodes_wake_recl_nam
+v.db.select zipcodes_wake_recl_nam
# dissolve:
-v.extract -d polbnda_italy_recl_nam out=pol_italy_regions
+v.extract -d input=zipcodes_wake_recl_nam output=zipcodes_wake_regions
</pre></div>
<p>
-produces a new vector map with common boundaries dissolved where the reclassed
+This produces a new vector map with common boundaries dissolved where the reclassed
attributes of adjacent (left/right) areas are identical.
<h3>Remove islands from polygon map</h3>
<div class="code"><pre>
-v.extract in=map_with_islands out=maps_without_islands cats=1-99999
+v.extract input=map_with_islands output=maps_without_islands cats=1-99999
# and/or
v.extract -d in=map_with_islands out=maps_without_islands
</pre></div>
<h3>Extract 3 random areas from geology map</h3>
-<p><div class="code"><pre>
+<p>
+<div class="code"><pre>
v.extract input=geology output=random_geology type=area random=3
</pre></div>
-will create new map with three random categories matching areas.
+This creates a new map with three random categories matching areas.
Note that there may be more than one feature with the same category.
<h2>SEE ALSO</h2>
More information about the grass-commit
mailing list