How to Create an Empty Vector in R

Empty vectors in R are the vectors whose length is zero. There are several ways to create empty vectors and then add elements to them. Vector is a basic data structure that contains elements of the same type. Let’s see how to create or initialize the empty vector in R.

How to Create an Empty Vector in R

There are the following ways to create an empty vector.

  1. Using vector() method
  2. Using c() method
  3. Using numeric() method
  4. Using rep() method
  5. Assigning NULL to an existing vector.

Create an empty Vector using the vector() method

To create an empty vector in R, use the basic vector() method, and don’t pass any parameter. By default, it will create an empty vector.

rv <- vector()
rv

Output

logical(0)

To check the length of the vector, use the length() method.

rv <- vector()
length(rv)

Output

[1] 0

The length() method will return the length of the vector object passed in the argument.

Now, you can add elements to the vector.

rv <- vector()
length(rv)
cat("After adding elements to an empty vector", "\n")
rv <- c(1:7)
rv
length(rv)

Output

[1] 0
After adding elements to an empty vector
[1] 1 2 3 4 5 6 7
[1] 7

And you can see from the output that we have added the elements to the vector.

Using the c() method to create an empty Vector

The c() method is mainly used for creating a vector in R. We can also use the c() method to empty the vector.

rv <- c()
rv
cat("length of rv : ", length(rv), "\n")
is.null(rv)

Output

NULL
length of rv : 0
[1] TRUE

As you can see, we created an empty vector using the c() function.

Using numeric() function

The numeric() function in R creates a double-precision vector of the length specified in the argument with all values zero.

So, we will create a vector with 0 length using the numeric() function.

rv <- numeric(0)
rv
cat("length of rv : ", length(rv), "\n")

Output

numeric(0)
length of rv : 0

Using rep( ) function

The rep() function replicates the values in the input data. It is a generic function.

rv <- rep(NULL, 0)
rv
cat("length of rv : ", length(rv), "\n")

Output

NULL
length of rv : 0

Here, you can use the is.null() function to check if the vector is NULL or not. The is.null() function returns a boolean vector that is either TRUE or FALSE.

You can also create an empty vector with the rep() function and NA. The “NA” in R designates a missing value, also known as Not Available.

rv <- rep(NA, 0)
rv
length(rv)
is.null(rv)

Output

logical(0)
[1] 0
[1] FALSE

As you can see that the rep() function with NA returns an empty vector, but it has not NULL value.

Assigning NULL to an existing vector

If you assign any vector to a NULL value, then that existing vector will become empty of NULL type.

rv <- 1:5
rv
length(rv)
rv <- NULL
rv
length(rv)
is.null(rv)

Output

[1] 1 2 3 4 5
[1] 5
NULL
[1] 0
[1] TRUE

First, we initialized a vector with five elements and then assign the NULL value to empty the vector of type NULL.

Conclusion

We have seen many ways to create an empty vector, and based on your requirements, and you can use one of the above approaches. You can use the c() function, vector() method, rep() or assign a NULL value to the existing vector or initialize the vector with NULL.

See also

How to Create Empty DataFrame in R

How to Check Data type in R

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