Example: Check Positive, Negative or Zero
# In this program, we input a number
# check if the number is positive or
# negative or zero and display
# an appropriate message
num = as.double(readline(prompt="Enter a number: "))
if(num > 0) {
print("Positive number")
} else {
if(num == 0) {
print("Zero")
} else {
print("Negative number")
}
}
Output 1
Enter a number: -9.6 [1] "Negative number"
Output 2
Enter a number: 2 [1] "Positive number"
A number is positive if it is greater than zero.
We check this in the expression of if. If it is FALSE, the number will either be zero or negative.
This is also tested in subsequent expression.