wilcoxonTest: Wilcoxon Signed Rank and Rank Sum Tests

Description Usage Arguments Value Note Author(s) Examples

View source: R/wilcoxonTest.R

Description

Perform a Wilcoxon signed rank test for a paired sample or a Wilcoxon rank sum test for independent samples on variables of a data set. The output is printed as a LaTeX table that mimics the look of SPSS output (version <24).

Usage

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wilcoxonTest(data, variables, group = NULL, exact = FALSE)

## S3 method for class 'wilcoxonTestSPSS'
print(x, digits = 2:3, statistics = c("ranks", "test"), ...)

Arguments

data

a data frame containing the variables.

variables

a character vector specifying numeric variable(s) to be used. If group is NULL, the Wilcoxon signed rank test is performed and this should be a character vector specifying two numeric variables which contain the paired observations. If a grouping variable is specified in group, the Wilcoxon rank sum test is performed and this should be a character string specifying the numeric variable of interest.

group

a character string specifying a grouping variable for the Wilcoxon rank sum test, or NULL.

exact

a logical indicating whether the Wilcoxon rank sum test should also return the p-value of the exact test. The default is FALSE. Note that the p-value of the asymptotic test is always returned.

x

an object of class "wilcoxonTestSPSS" as returned by function wilcoxonTest.

digits

an integer vector giving the number of digits after the comma to be printed in the LaTeX tables. The first element corresponds to the number of digits in table with the summary of the ranks, and the second element corresponds to the number of digits in the table for the test.

statistics

a character vector specifying which LaTeX tables should be printed. Available options are "ranks" for a summary of the ranks and "test" for test results. The default is to print both tables.

...

currently ignored.

Value

An object of class "wilcoxonTestSPSS" with the following components:

statistics

a data frame containing the relevant information on the ranks.

test

a list containing the results of the Wilcoxon signed rank test (only paired-sample test).

variables

a character vector containing the name(s) of the relevant numeric variable(s).

n

an integer giving the number of observations (only paired-sample test).

w

numeric; the Wilcoxon rank sum test statistic (only independent-samples test).

asymptotic

a list containing the results of the Wilcoxon rank sum test using the normal approximation (only independent-samples test).

exact

a list containing the test statistic of the exact Wilcoxon rank sum test test, and if requested the corresponding p-value (only independent-samples test).

group

a character string containing the name of the grouping variable (only independent-samples test).

type

a character string giving the type of Wilcoxon test performed "paired" or "independent").

The print method produces a LaTeX table that mimics the look of SPSS output (version <24).

Note

The Wilcoxon rank sum test also reports the value of the equivalent Mann-Whitney U test statistic.

Author(s)

Andreas Alfons

Examples

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## paired sample

# load data
data("Exams")

# test whether grades differ between the
# regular exam and the resit
wilcoxonTest(Exams, c("Regular", "Resit"))


## independent samples

# load data
data("Eredivisie")

# test whether market values differ between Dutch and foreign
# players
wilcoxonTest(Eredivisie, "MarketValue", group = "Foreign")

r2spss documentation built on Nov. 25, 2021, 1:06 a.m.