Decision making in programming allows us to control the flow of execution based on specific conditions. In R, various decision-making structures help us execute statements conditionally. These include:
- if statement
- if-else statement
- if-else-if ladder
- nested if-else statement
- switch statement
1. if Statement
The if statement evaluates a condition. If the condition is TRUE, the associated statement is executed. If the condition is FALSE, the statement is skipped.
Syntax:
if (condition) {
# execute this statement
}
Flow Chart:
Example:
a <- 76
b <- 67
if (a > b) {
c <- a - b
print("condition a > b is TRUE")
print(paste("Difference between a, b is:", c))
}
if (a < b) {
c <- a - b
print("condition a < b is TRUE")
print(paste("Difference between a, b is:", c))
}
Output:
[1] "condition a > b is TRUE"
[1] "Difference between a, b is: 9"
2. if-else Statement
The if-else statement executes one block if the condition is TRUE and another if it is FALSE.
Syntax:
if (condition) {
# execute this statement
} else {
# execute this statement
}
Flow Chart:
Example :
a <- 67
b <- 76
if (a > b) {
c <- a - b
print("condition a > b is TRUE")
print(paste("Difference between a, b is:", c))
} else {
c <- a - b
print("condition a > b is FALSE")
print(paste("Difference between a, b is:", c))
}
Output:
[1] "condition a > b is FALSE"
[1] "Difference between a, b is : -9"
3. if-else-if Ladder
This structure chains multiple conditions together. Each condition is evaluated in sequence. If a condition is TRUE, its block is executed. Otherwise, the next condition is checked.
Syntax:
if (condition1) {
# execute this statement
} else if (condition2) {
# execute this statement
} else {
# execute this statement
}
Flow Chart:
Example :
a <- 67
b <- 76
c <- 99
if (a > b && b > c)