If you have a large dataset to analyze, condensing a vast dataset with 30+ columns and thousands of rows will get tough. To solve this problem, you can use either head() or tail() function. It gives you a snapshot of that large dataset. In this tutorial, we will see how to use a head() function with different R data types.
head in R
The head() is a built-in R function that returns the first part of a Vector, Matrix, Table, data frame, or function. The head() is a generic function that can be extended in other classes. To get the first part of the object in R, use the head() function.
head(x, n, …)
The x is an object that can be a vector, Matrix, table, or data frame.
The n is a positive single integer. If positive or zero, size for the resulting object: number of elements for a vector.
Implementation of R head() function
To create a data frame in R, use the data.frame() function. We passed the named vector as an argument, returning the data frame. Now, let’s fetch the first three rows of the data frame using the head() 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("First three rows of data frame", "\n") head(df, 3)
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 First three rows of data frame c1 c2 c3 c4 c5 1 a e i m q 2 b f j n r 3 c g k o s
While using the head() function, we passed 3: a positive integer as an argument, which indicates the first 3 parts or, in our case, the first 3 rows of the data frame.
Using head() function on Vector
Applying the head() function to a Vector will return the number of elements equal to the n parameter of the head() function.
rv <- 1:10 rv cat("First five integers of vector", "\n") head(rv, 5)
 1 2 3 4 5 6 7 8 9 10 First five integers of vector  1 2 3 4 5
In this example, the n parameter of the head() function is 5, which means it will return the first five elements of the vector, which it did in the output.
Using head() function on Matrix()
To create a matrix in R, use the Matrix () function. The nrow and ncol properties define the dimension of the Matrix.
Let’s create a matrix of 5 X 3 and fetch the first 3 rows of the Matrix using the head() function.
rv <- 1:15 mtrx <- matrix(rv, nrow = 5, ncol = 3) mtrx cat("Using head() function to get first 3 rows", "\n") head(mtrx, 3)
[,1] [,2] [,3] [1,] 1 6 11 [2,] 2 7 12 [3,] 3 8 13 [4,] 4 9 14 [5,] 5 10 15 Using head() function to get first 3 rows [,1] [,2] [,3] [1,] 1 6 11 [2,] 2 7 12 [3,] 3 8 13
We used the head() function and passed the Matrix and number of rows as arguments, and it returned the Matrix with the first three rows.
Using head() function on built-in dataset
We will import the USArrests inbuilt R dataset and use that dataset’s head() function.
To import the dataset as a data frame, use the following code.
df <- datasets::USArrests
Now, use the head() function to get the first five rows of the dataset.
df <- datasets::USArrests head(df, 5)
Murder Assault UrbanPop Rape Alabama 13.2 236 58 21.2 Alaska 10.0 263 48 44.5 Arizona 8.1 294 80 31.0 Arkansas 8.8 190 50 19.5 California 9.0 276 91 40.6
As you can see that we only get the first five rows of the dataset.
That is it for the head() function in R.
Krunal Lathiya is an Information Technology Engineer by education and web developer by profession. He has worked with many back-end platforms, including Node.js, PHP, and Python. In addition, Krunal has excellent knowledge of Data Science and Machine Learning, and he is an expert in R Language. Krunal has written many programming blogs, which showcases his vast expertise in this field.