NAME¶

v.normal - Tests for normality for points.

KEYWORDS¶

vector, statistics

SYNOPSIS¶

v.normal v.normal help v.normal [-rql] map=string tests=range[, range,...] column=string [--verbose] [--quiet]

Flags:¶

-r

 

Use only points in current region

-q

 

Quiet

-l

 

lognormal

--verbose

 

Verbose module output

--quiet

 

Quiet module output

Parameters:¶

map=string

 

point vector defining sample points

tests=range[,range,...]

 

Lists of tests (1-15): e.g. 1,3-8,13

column=string

 

Attribute column

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¶

v.random random n=200 v.db.addtable random col="elev double precision" v.what.rast random rast=elevation.10m col=elev v.normal random tests=1-3,14 col=elev computes 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.

SEE ALSO¶

v.univar

AUTHOR¶

James Darrell McCauley , when he was at: Agricultural Engineering Purdue University Last changed: $Date: 2011-11-08 12:29:50 +0100 (Tue, 08 Nov 2011) $ Full index © 2003-2014 GRASS Development Team