Geografic-Information-System/display/d.vect.thematic/d.vect.thematic.html

<h2>DESCRIPTION</h2>

<em>d.vect.thematic</em> draws thematic choropleth vector maps based 
on an attribute column or an expression involving several columns. 
It takes a list of class <b>breaks</b> (excluding the minimum and maximum 
values) and a list of <b>colors</b> to apply to the classes (has to be the 
number of class breaks + 1).
<p>
Instead of a list of class breaks, the user can also chose a
classification <b>algorithm</b> and a number of classes
(<b>nbclasses</b>). See the
<em><a href="v.class.html">v.class</a></em> for more information on
these different algorithms.


<h2>NOTES</h2>

The <b>-l</b> flag instructs the module to print legend information
in vector legend format as described in <em><a href="d.legend.vect.html">d.legend.vect</a></em>
 to standard output for further use in graphical software.
When combined with the verbose flag, the legend information will
be extended with some additional statistical information. If the
<b>-n</b> flag is set, the module will only print the legend 
information without drawing the map.

<p>Option <b>legendfile</b>, is deprecated, instead
use the GRASS_LEGEND_FILE environmental variable
(see <em><a href="d.legend.vect.html">d.legend.vect</a></em>)
to save legend into a file.
Flag <b>-e</b> is deprecated, instead use verbose flag.

<h2>EXAMPLES</h2>

<h3>Thematic map with classes</h3>

<div class="code"><pre>
d.vect.thematic -l map=communes3 column=pop \
  breaks=111393.250000,222785.500000,334177.750000 \
  colors="255:0:0,0:255:0,0:0:255,0,0,0"
</pre></div>

<h3>Thematic map with calculated class breaks</h3>

The following example uses a calculated attribute (<tt>density = 
pop/area</tt>) and the standard deviation algorithm to calculate class 
breaks for 5 classes:

<div class="code"><pre>
d.vect.thematic -l map=communes2 column=pop/area algorithm=std \
  nbclasses=5 colors="0:0:255,50:100:255,255:100:50,255:0:0,156:0:0"
</pre></div>

<h3>Thematic map with legend</h3>

Example for the North Carolina sample dataset, colorizing basin polygons by
average elevation and displaying school capacity:

<div class="code"><pre>
# create watersheds from elevation map
g.region raster=elevation
r.watershed elevation=elevation threshold=10000 basin=basins_10k

# convert raster to vector
r.to.vect input=basins_10k output=basins_10k type=area column=basin_num

# upload raster statistics to each polygon in vector map
v.rast.stats map=basins_10k raster=elevation column_prefix=elev

# open a graphical display
d.mon wx0

# draw thematic polygons and specify legend title
d.vect.thematic map=basins_10k column=elev_average algorithm=int \
  nclasses=5 colors=0:195:176,39:255:0,251:253:0,242:127:11,193:126:60 \
  legend_title="Average elevation (m)"

# draw thematic points and specify legend title
d.vect.thematic map=schools_wake@PERMANENT column=CORECAPACI algorithm=std \
  nclasses=3 colors=149:203:255,45:143:240,0:81:161 icon=basic/circle size=15 \
  legend_title="School capacity"

# and finally draw legend
d.legend.vect -b at=2,80 font=Sans symbol_size=25
</pre></div>

<center>
<a href="d_vect_thematic.png">
<img src="d_vect_thematic.png" alt="d_vect_thematic example" width="600"></a>
<br>
<i>Thematic map of average elevation and school capacity</i>
</center>

<h2>SEE ALSO</h2>

<em>
<a href="v.class.html">v.class</a>,
<a href="d.legend.vect.html">d.legend.vect</a>,
<a href="d.vect.html">d.vect</a>,
<a href="d.graph.html">d.graph</a>,
<a href="v.univar.html">v.univar</a>
</em>

<p>
Check also Python module from
AddOns: <em><a href="https://grass.osgeo.org/grass7/manuals/addons/d.vect.thematic2.html">d.vect.thematic2</a></em>

<h2>AUTHOR</h2>

Moritz Lennert

<p>
<i>Last changed: $Date$</i>