A **two-way table** is a type of table that displays the frequencies for two categorical variables.

For example, the following two-way table shows the results of a survey that asked 100 people which sport they liked best: baseball, basketball, or football.

The rows display the gender of the respondent and the columns show which sport they chose:

This tutorial provides several examples of how to create and work with two-way tables in R.

**Example 1: Create a Two Way Table from Scratch**

The following code shows how to create a two way table from scratch using the **as.table()** function:

#create matrix data <- matrix(c(13, 23, 15, 16, 20, 13), ncol=3) #specify row and column names of matrix rownames(data) <- c('Male', 'Female') colnames(data) <- c('Baseball', 'Basketball', 'Football') #convert matrix to table data <- as.table(data) #display table data Baseball Basketball Football Male 13 15 20 Female 23 16 13

**Example 2: Create a Two Way Table from Data**

The following code shows how to create a two-way table from a data frame:

#create data frame df <- data.frame(sport=c('Base', 'Base', 'Bask', 'Foot', 'Foot'), gender=c('Male', 'Female', 'Male', 'Male', 'Female')) #view data frame df #create two way table from data frame data <- table(df$gender, df$sport) #display two way table data Base Bask Foot Female 1 0 1 Male 1 1 1

**Example 3: Calculate Margin Sums of a Two Way Table**

The following code shows how to calculate margin sums of a two-way table using the **margin.table()** function:

#create matrix of data data <- matrix(c(13, 15, 20, 23, 16, 13), ncol=3) rownames(data) <- c('Male', 'Female') colnames(data) <- c('Baseball', 'Basketball', 'Football') #find sum of genders margin.table(data, margin=1) Male Female 49 51 #find sum of sports margin.table(data, margin=2) Baseball Basketball Football 28 43 29

**Example 4: Visualize Two Way Table Frequencies**

One way to visualize the frequencies in a two way table is to create a **barplot**:

barplot(data, legend=True, beside=True, main='Favorite Sport by Gender')

Another way to visualize the frequencies in a two way table is to create a **mosaic plot**:

mosaicplot(data, main='Sports Preferences', xlab='Gender', ylab='Favorite Sport')

You can find more R tutorials on this page.