模块课程（2/2）
条件和循环
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'.
显示提示
Verifica score >= 60 e assegna status <- 'Pass' o status <- 'Fail'
3 次尝试后可用的解决方案
Write a for loop that iterates over the sequence 1:5 and prints each value using the print() function.
显示提示
Usa la sintassi: for (i in 1:5) { print(i) }
3 次尝试后可用的解决方案
Given the vector v, write a for loop that iterates over each element and prints its double (val * 2) using print().
显示提示
Loop through elements of v: for (val in v) { print(val * 2) }
3 次尝试后可用的解决方案
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.
显示提示
Use the function: results <- ifelse(scores >= 60, 'Pass', 'Fail')
3 次尝试后可用的解决方案
Use a while loop to double the value of x until it exceeds 50. Also increment the counter variable at each iteration.
显示提示
Use a while loop (x <= 50) and update both x and counter inside the curly braces.
3 次尝试后可用的解决方案