MATLAB Control Statements

What are control statements?

The name itself suggests that something is being controlled, these control statements decide or alter the flow of execution ina program. In program, we often need to modify or alter few lines of code, these control statement helps to perform this type of task.

Four categories of control statements are sequence control statements, decision control statements, repetition control statements (looping statements), and case control statements.

MATLAB control statements.

MATLAB Control Statements

If…end

If…end statement helps to execute a block of code by satisfying a condition. The condition is defined by user at the time of coding. This if… block of code is closed with the keyword “end”. We can also use elseif, else if further conditioning is required.

Let us look at the syntax and few examples below.

Syntax:

 if exp1
 set of statements
 end 

Flowchart:

MATLAB Control Statements

Example:

 j = 10;
 if j ~= 0
 disp('Nonzero value')
 end 

Output:

Nonzero value

If-else…end statement

This control statement executes at most one no. of commands on which condition evaluates true, and a default block is evaluated if conditions are not met.

The control flows in this direction à if clauseà1stelseif clause à 2ndelseif clause àelse clause.

Let us look at the syntax and few examples below.

Syntax:

 if exp1
             statements block
 else
             Statements block
 end 

Flowchart:

MATLAB Control Statements

Example:

 If size(d) is equal to size(f), arrays are concatenated otherwise an empty array is returned as output.
 d = ones(2,3);
 f = rand(3,4,5);
 ifisequal(size(d),size(f))
    k = [d; f];
 else
 disp('d and f are unequal.')
    k = [];
 end 

Output:

d and f are not the same size.

If-elseif-else….end

This control statement is the extended version of previous control statement, here we keep on adding elseif clause according to our requirement.

Let us look at the syntax and few examples below.

Syntax:

 If exp1
             Statements block
 elseif exp2
             Statements block
 else
             Statements block
 End 

Flowchart:

MATLAB Control Statements

Example:

 x = 20;
 min = 2;
 max = 6;
 if (x >= min) && (x <= max)
 disp('within specified range')
 elseif (x > max)
 disp('exceeds maximum ')
 else
 disp(' is below minimum')
 end 

output:

exceeds maximum

Nested if-else

Nested if-else is used when we decide to condition set of statements inside statements, but each if clause requires the end keyword. Let us look at the syntax and few examples below.

Syntax:

 if exp1  
     Statements block 
     if expression  
     Statements block 
     else  
     Statements block 
     end  
 elseif exp2  
     Statements block 
     if expression  
     Statements block 
     end  
 else   
     Statements block 
 end 

At first expression-1 is checked, the following set of statements are executed then control flows to if-else block. Elseif expression2 is further checked weather the condition gets satisfied or not. If none of the above condition is satisfied then at last else-block is executed with the end keyword.

Flowchart:

MATLAB Control Statements

Example:

 k =900;
 i=800;
 if( k ==900)
 if(i==800)
 fprintf('Value of k is 900 and i is 800\n');
 end
 end
 fprintf('value of k is : %d\n', k );
 fprintf('value of i is : %d\n',i); 

output:

 Value of a is 900 and b is 800
 value of a is : 900
 value of b is : 800 

Switch Statement

Switch statement can be an alternative of if-else statements, it is used to test a input against set of rules already defined. This control statement executes one of the several group of statements.

Let us look at the syntax and few examples below.

Syntax:

 switch switch_expr  
     case case_exp1  
         set of Statements  
     case case_exp2  
         set of Statements  
     case case_exp..N  
         set of Statements    
     otherwise  
         set of Statements  
 end   

Flowchart:

MATLAB Control Statements

Example:

 % program to convert number to string
 a = input('enter a number from 1 to 7  : ')  
 switch  a  
     case 1  
         disp('number in wordsàone')  
     case 2  
         disp(' number in wordsàtwo')  
     case 3  
         disp(' number in wordsàthree')  
     case 4  
         disp(' number in wordsàfour')  
     case 5  
         disp(' number in wordsàfive')  
     case 6  
         disp(' number in wordsàsix')  
     case 7  
         disp(' number in wordsàseven')  
     otherwise  
         disp('not a valid number')  
 end 

Output:

 enter a number: 4
 number in wordsàfour 



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