NAME
s.probplot - Normal probability plot of a GRASS site list.
(GRASS Sites Program)
SYNOPSIS
s.probplot
s.probplot help
s.probplot [-alq] sites=name
width=value [graph=name]
DESCRIPTION
s.probplot
does normal or lognormal probability plots of site values.
OPTIONS
Flags:
- -a
- Use all sites found in the named sites file, rather than
limiting output to sites falling within the current geographic region.
- -l
- Lognormal probability plot instead of normal.
- -q
- Quiet. Cut out the chatter.
Parameters:
- sites=name
- Name of an existing sites file.
- width=value
- Width of bins.
- graph=name
- Basename to save graphing data/commands files.
Graphs are saved in the current working directory with
the extensions .gp and .dat
NOTES
The plotting program can be selected by setting the environment
variable GRASS_GNUPLOT .
EXAMPLE
Given a sites file named example in the following format:
83.8|92.2|3.5689
83.8|82.2|3.9269
83.8|80.2|3.5389
83.8|69.2|3.7452
Suppose that we wish to examine normality of the site values (third column).
The first step is to examine minimum and maximum and determine with
the histogram bin width using s.univar:
-
s.univar -gq sites=example
This command outputs:
n=216
min=1.489
max=3.9419
...
along with other useful statistics. For this range and number of
observations, we randomly select 0.1 as the histogram bin width. Then,
the following command graphs a probability plot and saves it in the
current working directory with a basename of myplot:
-
s.probplt -q sites=example width=0.1 graph=myplot
To view the graph again, try
-
gnuplot myplot.gp
Using gnuplot, the graphs may be output as
PostScript, LaTeX, FrameMaker MIF, or many other formats.
SEE ALSO
s.univar
s.normal
gnuplot
BUGS
Please send all bug fixes and comments to the author
or the grass development team.
http://www.geog.uni-hannover.
AUTHOR
James Darrell McCauley
<darrell@mccauley-usa.com>,
when he was at:
Agricultural
Engineering
Purdue University
Last changed: $Date$