What is colon operator in R
This recipe explains what is colon operator in R
Recipe Objective
Colon operator (":") in R is a function that generates regular sequences. It is most commonly used in for loops, to index and to create a vector with increasing or decreasing sequence.
To look at the detailed R documention of the colon operator:
?":"
It is a binary operator i.e. it takes two arguments.
Syntax: a:bwhere:
a is the starting value of sequence ; b is the end value of the sequence
It generates a sequence from a to b in steps of 1 or -1 where value of b is included in the sequence.
This recipe is going to demonstrate 2 use cases of ":" operator
- Creating a sequential vector
- For loop
1. Creating a sequential vector
#in increasing sequence
vector_in = 1:9
vector_in
1 2 3 4 5 6 7 8 9
#in decreasing sequence
vector_de = 1:-9
vector_de
1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9
2. For loop
It is often used with the length() function in for loop to excecute a particular function on every element of a vector.
Example: we will square the elements of the vector using ":" and for loop
#creating a function to square the elements of a vector
square_ = function(x){
for (i in 1:length(x)){
print(i^2)
}
}
# giving vector_in as an arguement to get the squares of the element
square_(vector_in)
[1] 1 [1] 4 [1] 9 [1] 16 [1] 25 [1] 36 [1] 49 [1] 64 [1] 81
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