How to Put margins on tables or arrays in R

How to Put margins on tables or arrays in R, We’ll show you how to use the addmargins function in R to add margins to tables or arrays.

The tutorial will include two examples of using the addmargins function to annotate margin values on table objects.

Let’s get this party started:

How to Put margins on tables or arrays in R

For this R tutorial, we’ll start with the data below:

data <- data.frame(x1 = c(LETTERS[1:3],      
"B", "B", "C")
x2 = letters[1:2])
data                                         

   x1 x2
1  A  a
2  B  b
3  C  a
4  B  b
5  B  a
6  C  b

Examine the preceding table. It shows that the example data frame has six rows and two variables.

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Based on these data, we can then create a table object (i.e. a contingency table).

tab <- table(data)                        
tab                                       

x2
x1  a b
  A 1 0
  B 1 2
  C 1 1

The preceding RStudio console output shows our table without margins.

Example 1: Assign Sum Margins to a Contingency Table Using the function addmargins()

Example 1, Will show how to use the addmargins function to add the sum of each row and column to a table’s margins.

Consider the R code below:

tab_sum <- addmargins(tab, FUN = sum)     
tab_sum                                      

x2
x1    a b sum
  A   1 0   1
  B   1 2   3
  C   1 1   2
  sum 3 3   6

As you can see, we have annotated another row and column with our data’s sum margins.

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Example 2: Assign Mean Margins to a Contingency Table Using the function addmargins()

We used the sum function in Example 1 to add margins to our contingency table.

However, other functions within the addmargins command can be used.

The R code below demonstrates how to annotate mean values to a table object:

tab_mean <- addmargins(tab, FUN = mean)   
tab_mean                                    

x2
x1       a   b mean
  A    1.0 0.0  0.5
  B    1.0 2.0  1.5
  C    1.0 1.0  1.0
  mean 1.0 1.0  1.0

The previous table has the same structure as Example 1. However, instead of sum margins, we have included mean margins this time.

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