watson: Watson's Test

In CircStats: Circular Statistics, from "Topics in Circular Statistics" (2001)

Description

Performs a Watson's goodness of fit test for the von Mises or circular uniform distribution.

Usage

watson(x, alpha=0, dist='uniform')

Arguments

x	vector of angular measurements in radians.
alpha	significance level of the test. Valid levels are 0.01, 0.05, 0.1. This argument may be ommited, in which case, a range for the p-value will be returned.
dist	distribution to test for. The default is the uniform distribution. To test for the von Mises distribution, set dist = 'vm'.

Value

NULL

Note

If dist = 'uniform', Watson's one-sample test for the circular uniform distribution is performed, and the results are printed to the screen. If alpha is specified and non-zero, the test statistic is printed along with the critical value and decision. If alpha is omitted, the test statistic is printed and a range for the p-value of the test is given.

If dist = 'vm', estimates of the population parameters are used to evaluate the von Mises distribution function at all data points, thereby arriving at a sample of approximately uniformly distributed data, if the original observations have a von Mises distribution. The one-sample Watson test is then applied to the transformed data as above.

References

Jammalamadaka, S. Rao and SenGupta, A. (2001). Topics in Circular Statistics, Section 7.2, World Scientific Press, Singapore.

Stephens, M. (1970). Use of the Kolmogorov-Smirnov, Cramer-von Mises and related statistics without extensive tables. Journal of the Royal Statistical Society, B32, 115-122.

See Also

circ.range, kuiper, rao.spacing, r.test, v0.test

Examples

# Generate data from the uniform distribution on the circle.
data <- runif(100, 0, 2*pi)  
watson(data)
# Generate data from a von Mises distribution.
data <- rvm(50, 0, 4) 
watson(data, 0.05, dist='vm')

Example output

Loading required package: MASS
Loading required package: boot

       Watson's Test for Circular Uniformity 
 
Test Statistic: 0.1058 
P-value > 0.10 
 

       Watson's Test for the von Mises Distribution 
 
Test Statistic: 0.0186 
Level 0.05 Critical Value: 0.113 
Do Not Reject Null Hypothesis 
 

CircStats documentation built on May 2, 2019, 2:24 a.m.