If the input number to seq() function is length 1 then the outputs between seq() and seq_along() will be different. Let’s deep dive into seq_along() function.
seq_along() function in R
The seq_along() in R is a built-in function that creates a vector that contains a sequence of numbers from 1 to the object’s length. Thus, the seq_along() function creates a sequence the same length of the argument passed, and in the context of a for loop, is used to more easily create the index to iterate over.
The seq_along(n) is equivalent to 1:length(n).
The seq_along() method takes a length from the length of this argument.
The seq_along() function returns an integer vector unless it is a long vector when it will be double.
 1 2 3 4 5  1 2 3 4 5
In this example, we are creating vectors using LETTERS. You can see that it returns the indices of the vector elements.
You can also use the c() function to create a Vector.
seq_along(c(11, 21, 19)) seq_along(c(1.1, 2.1, 1.9, 1.8)) seq_along(c(200, 4000))
 1 2 3  1 2 3 4  1 2
That’s it for this tutorial.