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

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 in the GRASS graphics window 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
g.gnuplot myplot.gp
Using g.gnuplot, the graphs may be output as PostScript, LaTeX, FrameMaker MIF, or many other formats.

SEE ALSO

s.univar
s.normal
gnuplot_info

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