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To implement complex algorithms and procedures in R, you need to be able to control which instructions to execute and how many times to repeat them.
Conditional Statements
In R, the fundamental conditional structure is based on if and else. The syntax is very similar to languages like JavaScript or C:
score <- 85
if (score >= 60) {
print("Passed!")
} else {
print("Failed.")
}
Curly braces {} define the blocks of code to run depending on the outcome of the boolean expression inside parentheses.
The for Loop
The for loop in R is used to iterate over elements in a sequence (such as a vector or list).
# Print numbers from 1 to 3
for (i in 1:3) {
print(i)
}
In R, the 1:3 syntax is a shorthand way to create the vector c(1, 2, 3).
We can also loop directly over the elements of an existing vector:
fruits <- c("apple", "banana", "cherry")
for (fruit in fruits) {
print(fruit)
}
The ifelse Function
In R, the ifelse() function is a vectorized version of the if-else statement. It allows you to apply a condition to an entire vector in a single operation, returning a vector of results.
scores <- c(55, 80, 45, 90)
# Se score >= 60 assegna "Pass", altrimenti "Fail"
results <- ifelse(scores >= 60, "Pass", "Fail")
print(results) # "Fail" "Pass" "Fail" "Pass"
The while Loop
The while loop is used to repeat a block of code as long as a specific condition remains true (TRUE). It is essential to ensure that the condition eventually becomes false to prevent infinite loops.
counter <- 1
while (counter <= 3) {
print(counter)
counter <- counter + 1
}
Try it yourself
Write an if-else conditional statement that checks if the variable score is greater than or equal to 60. If it is, set status to 'Pass', otherwise set it to 'Fail'.
Toon hint
Verifica score >= 60 e assegna status <- 'Pass' o status <- 'Fail'
Oplossing beschikbaar na 3 pogingen
Write a for loop that iterates over the sequence 1:5 and prints each value using the print() function.
Toon hint
Usa la sintassi: for (i in 1:5) { print(i) }
Oplossing beschikbaar na 3 pogingen
Given the vector v, write a for loop that iterates over each element and prints its double (val * 2) using print().
Toon hint
Loop through elements of v: for (val in v) { print(val * 2) }
Oplossing beschikbaar na 3 pogingen
Given the vector scores, use the ifelse() function to check which elements are greater than or equal to 60. Save the result (which will contain 'Pass' or 'Fail' for each element) in the variable results.
Toon hint
Use the function: results <- ifelse(scores >= 60, 'Pass', 'Fail')
Oplossing beschikbaar na 3 pogingen
Use a while loop to double the value of x until it exceeds 50. Also increment the counter variable at each iteration.
Toon hint
Use a while loop (x <= 50) and update both x and counter inside the curly braces.
Oplossing beschikbaar na 3 pogingen