v.normal1grass

Usage

Keywords

vector, statistics, points, point pattern

Overview

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

Examples

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

Source code

Available at: v.normal source code (history)

Accessed: Monday Feb 24 17:51:20 2025

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