How to print tables with absolute and relative values in R


In R, there are several ways to generate tables. while the table() function generates tables with absolute numbers, the prop.table() function returns tables with relative values (percentages). However, I couldn't find a function to return a table with both absolute and relative values.

In this blog post, I show how to generate such a table.

Generate a random dataframe

In the first code snippet, we generate a random dataframe with two variables: Sex and Age. As you can see, generating random dataframes is very easy and straightforward with Tyler Rinker's Wakefield package.

df <- r_data_frame(n=200, sex, age)

Write the function

My function tab.func() combines three R functions:

  • describe() from the Hmisc package to return an object of class describe containing absolute and relative frequency values of a factor variable. To access these values, we need to subset this object using $values. This will return a matrix with the desired values.

  • t() to transpose this matrix, and

  • as.table() to transform this matrix into a table.

tab.func <- function (x) {
  y <- as.table(t(Hmisc::describe(x)$values))
  colnames(y) <- c('**n**', '**%**')

(UPDATE: In version 4 of the Hmisc package, the describe() function was rewritten. My function only works up to version 3.17.4)

The double asterisks around n and % are Markdown code used to return bold text.

Deploy the function

In the following code snippet, we deploy this function to a categorial variable (Sex) which is part of the dataframe df.

mytable <- tab.func(df$Sex)

             caption = 'Table with absolute numbers and percentages')
n %
A Male, Female 96, 104

Finaly, we print this table with the kable() function from the knitr package.


About norbert

Biometrician at Clinical Trial Centre, Leipzig University (GER), with degrees in sociology (MA) and public health (MPH).
This entry was posted in Data Management and tagged . Bookmark the permalink.

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