seq_len in R: How to Create a Sequence from 1 to N

The seq_len() function in R is used to generate a sequence of integers from 1 to a specified length. For example, seq_len(5) will return 1, 2, 3, 4, 5.

This function is helpful in creating sequences when you need to generate indices or iterate over a sequence of numbers in loops and vectorized operations.

Syntax

seq_len(num)

Parameters

num: It is a specified number.

Return value

It returns integers from 1 up to n. If num is less than or equal to 0, seq_len() returns an empty integer vector.

Example 1: Usage of seq_len()

Usage of seq_len() function

seq_len(1)
seq_len(2)
seq_len(6)

Output

[1] 1
[1] 1 2
[1] 1 2 3 4 5 6

Example 2: Creating an empty sequence

num <- 0

seq_len(num)

Output

integer(0)

The “integer(0)” is a length zero sequence of integers.

In the past, we used the colon sequence” notation to create sequences.

But there is a problem using this notation. The colon sequence notation can be dangerous as it does not handle the empty sequence case correctly.

num <- 0

1:num

Output

[1] 1  0

Example 3: Creating an index of a vector

Firstly, create a vector using the c() function and then find its length using the length() function, and then pass the output to the seq_len() function.

Creating an index of a vector

vec <- c(11, 18, 19, 21, 46)

lnt <- length(vec)

seq_len(lnt)

Output

[1] 1  2  3  4  5

You can see that we created a sequence of integers from 1 to lnt, where lnt is the length of the vector vec.

See also

seq() in r

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