ELSE IF Statement in R

Introduction to Else If in R

The ELSE IF statement in R is a powerful tool for handling complex decision-making scenarios. It allows you to check multiple conditions sequentially and execute different code blocks based on the results. The conditions are evaluated in order, and the first true condition's code block is executed. If none of the conditions are true, the code block associated with the ELSE statement is executed as a default. This construct helps avoid nested IF statements, improving code readability and maintainability. With ELSE IF, you can efficiently control the flow of your R programs, making them more structured and flexible.

Syntax

The ELSE IF statement in R provides a way to handle multiple conditions within a single control structure. Its syntax follows this pattern:

You can have multiple ELSE IF statements, each with its own condition and code block. The conditions are evaluated in the order they appear, and the code block associated with the first true condition will be executed. If none of the conditions are true, the code block associated with the ELSE statement will be executed.

In this code snippet, a variable named "score" is assigned a value of 85. The subsequent block of code uses the IF-ELSE IF statement in R to determine the corresponding grade based on the score. The program checks each condition sequentially. Since the score is 85, it doesn't satisfy the first condition (score >= 90). The program then moves to the next ELSE IF statement, and since 85 is greater than or equal to 80, it satisfies the condition (score >= 80), and the grade is assigned the value "B". As a result, the program prints "B" as the final output, which represents the grade based on the score.

Flowchart

A flowchart is a visual representation of the logical flow of a program. It helps in understanding the control flow and decision-making process. Here is a simplified flowchart demonstrating the logic of the ELSE IF statement in R:

The flowchart starts with the initial condition, and if it is true, the code block associated with it is executed. If the initial condition is false, the program moves to the next condition and checks if it is true. This process continues until a true condition is found, and the corresponding code block is executed. If none of the conditions are true, the code block associated with the ELSE statement is executed.The flowchart provides a visual representation of the decision-making process and helps in understanding the control flow of an ELSE IF statement in R.

In the given R code, the variable 'number' is initialized with the value -5. The subsequent IF-ELSE IF statements evaluate the value of 'number' to determine its sign. First, it checks if the 'number' is greater than 0. Since -5 is not greater than 0, it moves to the next ELSE IF condition. Then, it checks if the 'number' is less than 0. Since -5 satisfies this condition, the variable 'sign' is assigned the value "Negative." As the ELSE part is not executed in this case, the program directly proceeds to print the value of 'sign,' which is "Negative." Therefore, the output of this code snippet will be "Negative," indicating that the value of 'number' is a negative number.

Working of Else If Statement in R Programming

The ELSE IF statement in R allows you to handle multiple conditions and control the flow of your program accordingly. Here's an elaboration on how the ELSE IF statement works in R programming:

1. The program evaluates the first condition specified after the initial "if" statement. If the condition is true, the associated code block is executed, and the program moves on to the next statement after the entire ELSE IF construct.
2. If the first condition is false, the program evaluates the condition specified after the first "else if" statement. If this condition is true, the code block associated with it is executed, and the program proceeds to the next statement after the ELSE IF construct.
3. The program continues to evaluate each subsequent ELSE IF condition in order. If any of these conditions are true, the corresponding code block is executed, and the program moves on to the next statement after the ELSE IF construct.
4. If none of the conditions in the ELSE IF construct are true, the program executes the code block associated with the optional ELSE statement (if present). This code block serves as a default action to be executed when none of the conditions are satisfied.
5. Once the code block associated with a true condition (or the ELSE block) is executed, the program exits the entire ELSE IF construct, and the execution continues with the next statement after it.

It's important to note that the ELSE IF construct is evaluated sequentially, meaning that once a condition is found to be true, the remaining conditions are not evaluated. This makes the ELSE IF statement efficient for handling mutually exclusive conditions.

By using ELSE IF statements in your R programs, you can implement complex decision-making logic, avoid nested IF statements, and improve the readability and maintainability of your code.

In this R code snippet, the variable "hour" is assigned the value of 17. The program then goes through a series of conditions using the IF and ELSE IF statements to categorize the time of day based on the hour. First, it checks if the "hour" is less than 12. Since 17 is not less than 12, this condition is false, and the program moves on to the next ELSE IF condition. Here, it checks if the "hour" is less than 18. As 17 is less than 18, this condition is true, and the variable "time" is assigned the value "Afternoon". Since the ELSE statement is not reached, the program directly proceeds to the "print(time)" statement. As a result, "Afternoon" is printed on the screen, indicating that the given hour (17) corresponds to the "Afternoon" time of day.

R Else If Statement Examples

Example 1: Grade Classification

Example 2: Number Sign Classification

Example 3: Time of Day Classification