---
name: "v.normal"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/v.normal"
---

# v.normal(1grass)

Tests for normality for vector points.

## 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

## 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)

Accessed: Monday Feb 24 17:51:20 2025

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