head() function in R is one of the most useful functions that lets you quickly get a peek at the data you have in a R object. Using head() function in R, you can view the first elements in a vector, matrix, dataframe and other R objects. In this tutorial, we will use head() function to see the first elements in a vector, matrix, and dataframe with multiple examples.
View the first few elements in a vector using head() in R
First, let us use head() function to take a look at the top elements in a vector. We use seq() function to create a vector containing sequence of numbers.
my_vector <- seq(1000)
When we use head() function on the vector, it prints the first 6 elements in the vector by default.
head(my_vector) ## [1] 1 2 3 4 5 6
By using the argument n to the head function, we can specify the number of elements in the vector to print. In this example we use n=10 to see the first 10 elements in the vector.
head(my_vector, n = 10) ## [1] 1 2 3 4 5 6 7 8 9 10
See the first few elements in a matrix using head() in R
We can also use head() function to get a look at the first few rows of a matrix. Let us create a matrix using matrix() function.
my_matrix <- matrix(seq(1000), ncol=5)
By default, head() function prints the first 6 rows.
head(my_matrix) ## [,1] [,2] [,3] [,4] [,5] ## [1,] 1 201 401 601 801 ## [2,] 2 202 402 602 802 ## [3,] 3 203 403 603 803 ## [4,] 4 204 404 604 804 ## [5,] 5 205 405 605 805 ## [6,] 6 206 406 606 806
We can provide the number of rows we want to print as argument to head() function. In this example, we have provided n=3 to see the first 3 rows.
head(my_matrix, 3) ## [,1] [,2] [,3] [,4] [,5] ## [1,] 1 201 401 601 801 ## [2,] 2 202 402 602 802 ## [3,] 3 203 403 603 803
Get a peek at the top elements in a dataframe using head() in R
head() function also works with dataframes. By default, head() function applied to a dataframe shows the first 6 rows of the dataframe.
head(ChickWeight) ## weight Time Chick Diet ## 1 42 0 1 1 ## 2 51 2 1 1 ## 3 59 4 1 1 ## 4 64 6 1 1 ## 5 76 8 1 1 ## 6 93 10 1 1
With n argument to head() function, we can specify the number of rows to print. In this example, we ask head() function to print the first 3 rows of the dataframe.
head(ChickWeight, n=3) ## weight Time Chick Diet ## 1 42 0 1 1 ## 2 51 2 1 1 ## 3 59 4 1 1
Here we look at the first 10 rows of the dataframe.
head(ChickWeight, n=10) ## weight Time Chick Diet ## 1 42 0 1 1 ## 2 51 2 1 1 ## 3 59 4 1 1 ## 4 64 6 1 1 ## 5 76 8 1 1 ## 6 93 10 1 1 ## 7 106 12 1 1 ## 8 125 14 1 1 ## 9 149 16 1 1 ## 10 171 18 1 1
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