While Loop Syntax in R
Following is the syntax for While Loop in R programming:
while (condition) { Exp }
R While Loop Flowchart
Note: Remember to write a closing condition at some point otherwise the loop will go on indefinitely.
While Loop in R Programming Examples
Example 1:
Let’s go through a very simple example to understand the concept of while loop. You will create a loop and after each run add 1 to the stored variable. You need to close the loop, therefore we explicitely tells R to stop looping when the variable reached 10. Note: If you want to see current loop value, you need to wrap the variable inside the function print().
#Create a variable with value 1 begin <- 1
#Create the loop while (begin <= 10){
#See which we are
cat(‘This is loop number’,begin)
#add 1 to the variable begin after each loop begin <- begin+1 print(begin) }
Output:
This is loop number 1[1] 2
This is loop number 2[1] 3
This is loop number 3[1] 4
This is loop number 4[1] 5
This is loop number 5[1] 6
This is loop number 6[1] 7
This is loop number 7[1] 8
This is loop number 8[1] 9
This is loop number 9[1] 10
This is loop number 10[1] 11
Example 2:
You bought a stock at price of 50 dollars. If the price goes below 45, we want to short it. Otherwise, we keep it in our portfolio. The price can fluctuate between -10 to +10 around 50 after each loop. You can write the code as follow:
set.seed(123)
Set variable stock and price
stock <- 50 price <- 50
Loop variable counts the number of loops
loop <- 1
Set the while statement
while (price > 45){
Create a random price between 40 and 60
price <- stock + sample(-10:10, 1)
Count the number of loop
loop = loop +1
Print the number of loop
print(loop) }
Output:
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
cat(‘it took’,loop,’loop before we short the price. The lowest price is’,price)
Output:
