Note: This document is for an older version of GRASS GIS that has been discontinued. You should upgrade, and read the current manual page.

GRASS logo

NAME

v.normal - Tests for normality for vector points.

KEYWORDS

vector, statistics, points, point pattern

SYNOPSIS

v.normal
v.normal --help
v.normal [-rl] map=name [layer=string] tests=range[,range,...] column=name [--help] [--verbose] [--quiet] [--ui]

Flags:

-r
Use only points in current region
-l
Lognormality instead of normality
--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
tests=range[,range,...] [required]
Lists of tests (1-15)
E.g. 1,3-8,13
column=name [required]
Name of attribute column

Table of contents

DESCRIPTION

v.normal computes tests of normality on vector points.

NOTES

The tests that v.normal performs are indexed below. The tests that are performed are specified by giving an index, ranges of indices, or multiple thereof.
  1. Sample skewness and kurtosis
  2. Geary's a-statistic and an approximate normal transformation
  3. Extreme normal deviates
  4. D'Agostino's D-statistic
  5. Modified Kuiper V-statistic
  6. Modified Watson U^2-statistic
  7. Durbin's Exact Test (modified Kolmogorov)
  8. Modified Anderson-Darling statistic
  9. Modified Cramer-Von Mises W^2-statistic
  10. Kolmogorov-Smirnov D-statistic (modified for normality testing)
  11. Chi-Square test statistic (equal probability classes) and the number of degrees of freedom
  12. Shapiro-Wilk W Test
  13. Weisberg-Binghams W'' (similar to Shapiro-Francia's W')
  14. Royston's extension of W for large samples
  15. Kotz Separate-Families Test for Lognormality vs. Normality

EXAMPLE

Compute the sample skewness and kurtosis, Geary's a-statistic and an approximate normal transformation, extreme normal deviates, and Royston's W for the random vector points: 
g.region raster=elevation -p
v.random random n=200
v.db.addtable random column="elev double precision"
v.what.rast random rast=elevation column=elev
v.normal random tests=1-3,14 column=elev

SEE ALSO

v.univar

AUTHORS

James Darrell McCauley <darrell@mccauley-usa.com>,
when he was at: Agricultural Engineering Purdue University

SOURCE CODE

Available at: v.normal source code (history)

Latest change: Thursday Jan 26 14:10:26 2023 in commit: cdd84c130cea04b204479e2efdc75c742efc4843

Main index | Vector index | Topics index | Keywords index | Graphical index | Full index

© 2003-2024 GRASS Development Team, GRASS GIS 8.3.3dev Reference Manual