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  MATLAB 流程控制

  • 流程控制

    流程控制要求程序员应指定一个或多个要由程序评估或测试的条件，如果确定条件为真，则应指定要执行的一个或多个语句，如果条件为真，则可以选择要执行的其他语句。条件确定为假。以下是大多数编程语言中常见的典型决策结构的一般形式-
    c decision_making
    MATLAB提供以下类型的决策声明。

  • if...end

    语法- 
    
if <expression>
   % statement(s) will execute if the boolean expression is true 
   <statements>
end
    创建一个脚本文件并输入以下代码- 
    
a = 10;
% check the condition using if statement 
   if a < 20 
   % if condition is true then print the following 
      fprintf('a is less than 20\n' );
   end
fprintf('value of a is : %d\n', a);
    尝试一下
    运行文件时，它将产生以下结果- 
    
a is less than 20
value of a is : 10

  • if...else..end

    语法- 
    
if <expression>
   % statement(s) will execute if the boolean expression is true 
   <statement(s)>
else
   <statement(s)>
   % statement(s) will execute if the boolean expression is false 
end
    创建一个脚本文件并输入以下代码- 
    
a = 100;
% check the boolean condition 
   if a < 20 
      % if condition is true then print the following 
      fprintf('a is less than 20\n' );
   else
      % if condition is false then print the following 
      fprintf('a is not less than 20\n' );
   end
   fprintf('value of a is : %d\n', a);
    尝试一下
    运行文件时，它将产生以下结果- 
    
a is not less than 20
value of a is : 100

  • if...elseif...elseif...else...end

    语法- 
    
if <expression 1>
   % Executes when the expression 1 is true 
   <statement(s)>

elseif <expression 2>
   % Executes when the boolean expression 2 is true
   <statement(s)>

Elseif <expression 3>
   % Executes when the boolean expression 3 is true 
   <statement(s)>

else 
   %  executes when the none of the above condition is true 
   <statement(s)>
end
    创建一个脚本文件并输入以下代码- 
    
a = 100;
%check the boolean condition 
   if a == 10 
      % if condition is true then print the following 
      fprintf('Value of a is 10\n' );
   elseif( a == 20 )
      % if else if condition is true 
      fprintf('Value of a is 20\n' );
   elseif a == 30 
      % if else if condition is true  
      fprintf('Value of a is 30\n' );
   else
      % if none of the conditions is true '
      fprintf('None of the values are matching\n');
   fprintf('Exact value of a is: %d\n', a );
   end
    尝试一下
    运行文件时，它将产生以下结果- 
    
None of the values are matching
Exact value of a is: 100

  • 嵌套if

    在MATLAB中嵌套if-else语句始终是合法的，这意味着您可以在另一个if or elseif语句中使用一个if or elseif语句。
    语法- 
    
if <expression 1>
   % Executes when the boolean expression 1 is true 
   if <expression 2>
      % Executes when the boolean expression 2 is true    
   end
end
    创建一个脚本文件并输入以下代码- 
    
a = 100;
b = 200;
   % check the boolean condition 
   if( a == 100 )
   
      % if condition is true then check the following 
      if( b == 200 )
       
         % if condition is true then print the following 
         fprintf('Value of a is 100 and b is 200\n' );
      end
       
   end
   fprintf('Exact value of a is : %d\n', a );
   fprintf('Exact value of b is : %d\n', b );
    尝试一下
    运行文件时，它将产生以下结果- 
    
Value of a is 100 and b is 200
Exact value of a is : 100
Exact value of b is : 200

  • switch 语句

    MATLAB中switch语句的语法为-
    语法- 
    
switch <switch_expression>
   case <case_expression>
      <statements>
   case <case_expression>
      <statements>
      ...
      ...
   otherwise
      <statements>
end
    创建一个脚本文件并输入以下代码- 
    
grade = 'B';
   switch(grade)
   case 'A' 
      fprintf('Excellent!\n' );
   case 'B' 
      fprintf('Well done\n' );
   case 'C' 
      fprintf('Well done\n' );
   case 'D'
      fprintf('You passed\n' );
   case 'F' 
      fprintf('Better try again\n' );
   otherwise
      fprintf('Invalid grade\n' );
   end
    尝试一下
    运行文件时，它将产生以下结果- 
    
Well done

  • 嵌套 switch 语句

    MATLAB中switch语句的语法为-
    语法- 
    
switch(ch1) 
   case 'A' 
      fprintf('This A is part of outer switch');
      switch(ch2) 
         case 'A'
         fprintf('This A is part of inner switch' );
         
         case 'B'  
         fprintf('This B is part of inner switch' );
      end   
   case 'B'
      fprintf('This B is part of outer switch' );
end
    创建一个脚本文件并输入以下代码- 
    
a = 100;
b = 200;
switch(a) 
   case 100 
      fprintf('This is part of outer switch %d\n', a );
      switch(b) 
         case 200
            fprintf('This is part of inner switch %d\n', a );
      end
end

fprintf('Exact value of a is : %d\n', a );
fprintf('Exact value of b is : %d\n', b );
    尝试一下
    运行文件时，它将产生以下结果- 
    
This is part of outer switch 100
This is part of inner switch 100
Exact value of a is : 100
Exact value of b is : 200
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