wtest: Walter and Elwood's Test of Seasonality

Description Usage Arguments Details Value Author(s) References Examples

View source: R/wtest.R

Description

Tests for a seasonal pattern in Binomial data.

Usage

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wtest(cases, offset, data, alpha=0.05)

Arguments

cases

variable name for cases (“successes”).

offset

variable name for at-risk population (“trials”).

data

data frame (optional).

alpha

significance level (default=0.05).

Details

A test of whether monthly data has a sinusoidal seasonal pattern. The test has low power compared with the cosinor test.

Value

test

test statistic.

pvalue

p-value.

Author(s)

Adrian Barnett a.barnett<at>qut.edu.au

References

Walter, S.D., Elwood, J.M. (1975) A test for seasonality of events with a variable population at risk. British Journal of Preventive and Social Medicine 29, 18–21.

Barnett, A.G., Dobson, A.J. (2010) Analysing Seasonal Health Data. Springer.

Examples

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data(stillbirth)
# tabulate the total number of births and the number of stillbirths
freqs = table(stillbirth$month,stillbirth$stillborn)
data = list()
data$trials = as.numeric(freqs[,1]+freqs[,2])
data$success = as.numeric(freqs[,2])
# test for a seasonal pattern in stillbirth
test = wtest(cases='success', offset='trials', data=data)

season documentation built on June 3, 2021, 5:06 p.m.