tab (version 2.1.1)

tabfreq: Generate frequency tables for statistical reports

Description

This function creates an I-by-J frequency table and summarizes the results in a clean table for a statistical report.

Usage

tabfreq(x, y, latex = FALSE, xlevels = NULL, ylevels = NULL, yname = "Y variable", 
        test = "chi", decimals = 1, p.decimals = c(2, 3), p.cuts = 0.01, 
        p.lowerbound = 0.001, p.leading0 = TRUE, p.avoid1 = FALSE, n = FALSE, 
        compress = FALSE)

Arguments

x

Vector of values indicating group membership for columns of IxJ table.

y

Vector of values indicating group membership for rows of IxJ table.

latex

If TRUE, object returned will be formatted for printing in LaTeX using xtable [1]; if FALSE, it will be formatted for copy-and-pasting from RStudio into a word processor.

xlevels

Optional character vector to label the levels of x. If unspecified, the function uses generic labels.

ylevels

Optional character vector to label the levels of y. If unspecified, the function uses generic labels.

yname

Optional label for the y (row) variable.

test

Controls test of independence between x and y. "chi" for Pearson's chi-squared test, "fisher" for Fisher's exact test.

decimals

Number of decimal places for percentages.

p.decimals

Number of decimal places for p-values. If a vector is provided rather than a single value, number of decimal places will depend on what range the p-value lies in. See p.cuts input.

p.cuts

Cut-point(s) to control number of decimal places used for p-values. For example, by default p.cuts is 0.1 and p.decimals is c(2, 3). This means that p-values in the range [0.1, 1] will be printed to two decimal places, while p-values in the range [0, 0.1)

p.lowerbound

Controls cut-point at which p-values are no longer printed as their value, but rather

p.leading0

If TRUE, p-values are printed with 0 before decimal place; if FALSE, the leading 0 is omitted.

p.avoid1

If TRUE, p-values rounded to 1 are not printed as 1, but as >0.99 (or similarly depending on values for p.decimals and p.cuts).

n

If TRUE, the table returned will include sample sizes in the column headings.

compress

If y has only two levels, setting compress to TRUE will produce a single row for n (percent) for the higher level. For example, if y is gender with 0 for female, 1 for male, setting compress = TRUE will return a table with n (percent) for males only.

Value

• A character matrix with the requested frequency table. If you click on the matrix name under "Data" in the RStudio Workspace tab, you will see a clean table that you can copy and paste into a statistical report or manuscript. If latex is set to TRUE, the character matrix will be formatted for inserting into an Sweave or Knitr report using the xtable package [1].

Details

NA

References

1. Dahl DB (2013). xtable: Export tables to LaTeX or HTML. R package version 1.7-1, http://CRAN.R-project.org/package=xtable. Acknowledgment: This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0940903.

See Also

tabmeans tabcox tabglm tabgee

Examples

# Load in sample dataset d and drop rows with missing values
data(d)
d <- d[complete.cases(d),]

# Create labels for treatment group, sex, and race
groups <- c("Control", "Treatment")
sexes <- c("Female", "Male")
races <- c("White", "Black", "Mexican American", "Other")

# Compare sex distribution by group, with group as column variable
freqtable1 <- tabfreq(x = d$group, y = d$sex, xlevels = groups, ylevels = sexes, 
                      yname = "Sex")

# Same comparison, but compress table to single row and include sample size
freqtable2 <- tabfreq(x = d$group, y = d$sex, xlevels = groups, yname = "Male", 
                      compress = TRUE, n = TRUE)

# Compare sex distribution by race, with race as column variable
freqtable3 <- tabfreq(x = d$race, y = d$sex, xlevels = races, yname = "Sex", 
                      ylevels = sexes)

# Use rbind to create single table comparing sex and race in control vs. treatment group
freqtable4 <- rbind(tabfreq(x = d$group, y = d$sex, xlevels = groups, 
                            ylevels = sexes, yname = "Sex"),
                    tabfreq(x = d$group, y = d$race, xlevels = groups, 
                            ylevels = races, yname = "Race"))

# Click on freqtable1, freqtable2, freqtable3, and freqtable4 in the Workspace tab of 
# RStudio to see the tables that could be copied and pasted into a report or manuscript.
# Alternatively, setting the latex input to TRUE produces tables that can be inserted 
# into LaTeX using the xtable package.