d.vect.colhist - GRASS GIS manual

NAME

d.vect.colhist - Draws the histogram of values in a vector attribute column

KEYWORDS

SYNOPSIS

d.vect.colhist

d.vect.colhist --help

d.vect.colhist map=name [layer=string] column=name [where=sql_query] plot_output=name [bins=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

map=name [required]: Name of vector map; Or data source for direct OGR access
layer=string: Layer number or name; Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.; Default: 1
column=name [required]: Attribute column containing azimuth
where=sql_query: WHERE conditions of SQL statement without 'where' keyword; Example: income < 1000 and population >= 10000
plot_output=name [required]: Name for graphic output file for plot (extension decides format, - for screen); Name for output file; Default: -
bins=integer: Number of bins in histogram; Default: 30

DESCRIPTION
NOTE
EXAMPLE
AUTHOR

DESCRIPTION

d.vect.colhist draws a histogram of the values in a vector map attribute column. The user use the where option to only select a subset of the attribute table and can determine the number of bins (bars) used for the histogram. The plot_output parameter determines whether the result is displayed on screen (default) or exported to a graphics file.

NOTE

This is a quick and dirty solution using basic matplotlib. In future, this should be integrated into the g.gui, possibly together with the raster histogram tool.

EXAMPLE

Show the histogram of median age values in the census block map:

d.vect.colhist map=censusblk_swwake column=MEDIAN_AGE where="TOTAL_POP>0"

Histogram of median age values of census blocks

AUTHOR

Moritz Lennert

SOURCE CODE

Available at: d.vect.colhist source code (history)