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An **if** statement can be followed by an optional **else** statement which executes when the boolean expression is false.

The basic syntax for creating an **if...else** statement in R is −

if(boolean_expression) { // statement(s) will execute if the boolean expression is true. } else { // statement(s) will execute if the boolean expression is false. }

If the Boolean expression evaluates to be **true**, then the **if block** of code will be executed, otherwise **else block** of code will be executed.

x <- c("what","is","truth") if("Truth" %in% x) { print("Truth is found") } else { print("Truth is not found") }

When the above code is compiled and executed, it produces the following result −

[1] "Truth is not found"

Here "Truth" and "truth" are two different strings.

An **if** statement can be followed by an optional **else if...else** statement, which is very useful to test various conditions using single if...else if statement.

When using **if**, **else if**, **else** statements there are few points to keep in mind.

An

**if**can have zero or one**else**and it must come after any**else if**'s.An

**if**can have zero to many**else if's**and they must come before the else.Once an

**else if**succeeds, none of the remaining**else if**'s or**else**'s will be tested.

The basic syntax for creating an **if...else if...else** statement in R is −

if(boolean_expression 1) { // Executes when the boolean expression 1 is true. } else if( boolean_expression 2) { // Executes when the boolean expression 2 is true. } else if( boolean_expression 3) { // Executes when the boolean expression 3 is true. } else { // executes when none of the above condition is true. }

x <- c("what","is","truth") if("Truth" %in% x) { print("Truth is found the first time") } else if ("truth" %in% x) { print("truth is found the second time") } else { print("No truth found") }

When the above code is compiled and executed, it produces the following result −

[1] "truth is found the second time"

r_decision_making.htm

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