R if-else语句实例图解 _条件语句

【R if-else语句实例图解】该语句也称为嵌套if-else语句。 if语句后面是可选的else if … .. else语句。该语句用于在单个if … … else if语句中测试各种条件。当我们使用if … . else if … .. else语句时, 需要牢记一些关键点。这些要点如下：

if语句可以为零或一个else语句, 并且必须在其他if语句之后。
if语句可以包含许多其他if语句, 它们位于else语句之前。
一旦else if语句成功, 将不会测试其余的if if else。

If-else语句的基本语法如下：

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

流程图

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例子1

age < - readline(prompt="Enter age: ")age < - as.integer(age)if(age< 18) print("You are child")else if(age> 30) print("You are old guy")else print("You are adult")

输出

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例子2

marks=83; if(marks> 75){ print("First class")}else if(marks> 65){ print("Second class")}else if(marks> 55){ print("Third class")}else{ print("Fail")}

输出

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例子3

cat("1) For Addition\n")cat("2) For Subtraction\n")cat("3) For Division\n")cat("4) For multiplication\n")n1< -readline(prompt="Enter first number:")n2< -readline(prompt="Enter second number:")choice< -readline(prompt="Enter your choice:")n1< - as.integer(n1)n2< - as.integer(n2)choice< - as.integer(choice)if(choice==1){ sum < -(n1+n2) cat("sum=", sum)}else if(choice==2){ sub< -(n1-n2) cat("sub=", sub)}else if(choice==3){ div< -n1/n2 cat("Division=", div)}else if(choice==4){ mul< -n1*n2 cat("mul=", mul)}else{ cat("wrong choice")}

输出

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例子4

x < - c("Hardwork", "is", "the", "key", "of", "success")if("Success" %in% x) {print("success is found in the first time")} else if ("success" %in% x) {print("success is found in the second time")} else {print("No success found")}

输出

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例子5

n1=4n2=87n3=43n4=74if(n1> n2){ if(n1> n3& & n1> n4){largest=n1 }}else if(n2> n3){ if(n2> n1& & n2> n4){largest=n2 }}else if(n3> n4){ if(n3> n1& & n3> n2){largest=n3 }}else{ largest=n4}cat("Largest number is =", largest)

输出