tail() in R: How to Get Last Part of R Object

If you have a large dataset to analyze, it will get tough to condense a huge dataset that has 30+ columns and have thousands of rows. To solve this problem, you can use the head() or tail() function. It gives you a snapshot of that large dataset. In this tutorial, we will see how to use a tail() function with different R data types.

tail() in R

The tail() is a built-in R function that returns the last part of a vector, matrix, table, data frame, or function. To get the last part of the object in R, use the tail() function.  The tail() method in R is a generic function that can be extended in other classes.

Syntax

tail(x, n, …)

Parameters

The x is an object that can be a vector, matrix, table, or data frame.

The is a positive single integer. If positive or zero, size for the resulting object: number of elements for a vector.

Implementation of R tail() function

To create a data frame in R, use the data.frame() function. We passed the named vector as an argument, and it returns the data frame. Now, let’s fetch the last three rows of the data frame using the tail() function.

df <- data.frame(c1 = c("a", "b", "c", "d"),
                 c2 = c("e", "f", "g", "h"),
                 c3 = c("i", "j", "k", "l"),
                 c4 = c("m", "n", "o", "p"),
                 c5 = c("q", "r", "s", "t"))
df
cat("Last two rows of data frame", "\n")
tail(df, 2)

Output

   c1 c2 c3 c4 c5
1  a  e  i  m  q
2  b  f  j  n  r
3  c  g  k  o  s
4  d  h  l  p  t
Last two rows of data frame
   c1 c2 c3 c4 c5
3  c  g  k  o  s
4  d  h  l  p  t

While using the tail() function, we passed 2: a positive integer as an argument, which indicates the last 2 parts or, in our case, its first two rows of the data frame.

Using tail() function on Vector

If you apply the tail() function on a Vector, it will return the number of elements equal to the n parameter of the tail() function.

rv <- 1:10
rv
cat("Last five integers of vector", "\n")
tail(rv, 5)

Output

[1] 1 2 3 4 5 6 7 8 9 10
Last five integers of vector
[1] 6 7 8 9 10

In this example, the n parameter of the tail() function is 5, which means it will return the last five elements of the vector, which it did in the output.

Using tail() function on Matrix()

To create a matrix in R, use the matrix() function. The dimension of the Matrix is defined by nrow and ncol property.

Let’s create a matrix of 5 X 3 and fetch the last 2 rows of the matrix using the tail() function.

rv <- 1:15
mtrx <- matrix(rv, nrow = 5, ncol = 3)
mtrx
cat("Using tail() function to get the last 2 rows", "\n")
tail(mtrx, 2)

Output

     [,1] [,2] [,3]
[1,]  1    6    11
[2,]  2    7    12
[3,]  3    8    13
[4,]  4    9    14
[5,]  5   10    15
Using tail() function to get the last 2 rows
     [,1] [,2] [,3]
[4,]  4    9   14
[5,]  5   10   15

In this example, we used the tail() function and passed the matrix and number of rows as arguments, and it returns the matrix with the last two rows.

Using tail() function on built-in dataset

We will import the ChickWeight inbuilt R dataset and use the tail() function on that dataset.

To import the dataset as a data frame, use the following code.

df <- datasets::ChickWeight

Now, use the tail() function to get the last five rows of the dataset.

df <- datasets::ChickWeight
tail(df, 5)

Output

     weight Time Chick Diet
574   175   14    50    4
575   205   16    50    4
576   234   18    50    4
577   264   20    50    4
578   264   21    50    4

As you can see that we only get the last five rows of the dataset.

That is it for the tail() function in R.

Leave a Comment