While loop in MATLAB: Everything You Need to Know

Introduction

MATLAB is a scientific programming language that is used meticulously by developers for its educational value and relevance. Developed by MathWorks, MATLAB needs pre-licensing before usage for organizations and limited free-usage for students.

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Today, we are talking about the fundamentals of while loop in MATLAB which are condition functions that help in the execution of the statement when the condition satisfies. For a beginner-focused on learning about the basics of MATLAB, today we will entirely concentrate on the working of the while loop. 

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The While Loop in MATLAB

Used in iteration, the while loop is used when there is a need for continuous execution of the statement, as criteria are met. The statements that are executed need to have non-zero elements, and when the condition is false, the loop will stop. 

Syntax of while loop: 

while (condition)

  [perform code]

end

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Understanding the syntax and scope: 

• Here, ‘while’ stands as the keyword for the while loop/function.
• The condition statement is similar to a trigger that works only when the case is true.
• For a program that doesn’t satisfy the condition value anytime, the function never executes.
• Here, ‘end’ refers to the end of the program, which is generally handy when conditions aren’t met. 
• If a condition always meets in a program, using the while loop can set off an infinite loop chain entirely. 

Here’s an example: 

x = 20;

while (x<30)

fprintf (‘value of x: %d\n’, a);

x = x+1;

end

Understanding the function:

• First, the variable is defined with a certain value; here, it is 30.
• Second, we place the while loop and with the condition of it running until x is lesser than 30. Which means the loop would have a scope from x=20 to x=29. 
• The ‘fprintf’ function displays the value of x on the screen.
• Then, the next line increases the value of x every time it runs, by 1. 
• Therefore, the loop runs until 29 (i.e., 10 times, starting from 20) and then stops as x=30 isn’t lesser than 30. 

Based on the above explanation, the output of the above program would be: 

value of x: 20

value of x: 21

value of x: 22

value of x: 23

value of x: 24

value of x: 25

value of x: 26

value of x: 27

value of x: 28

value of x: 29

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Things to Remember:

• Non-scalar Expressions: These refer to the executed statements that generate a non-scalar or a combination of true and false cases. In such situations, the entire expression needs to be true for all cases, to get executed as a true statement in a while loop. For example: 

Given matrices A and B

A =                 B =

                    1     0            1     1

                    2     3            3     4

Here, the while (A < B) is true for cases where the corresponding A value is lesser than B, and here, the condition fails when A (1,1) since A1 (1) is not smaller than B1 (1). 

• Partial Evaluation of Expression Arguments: 

In MATLAB, expression generally consists of variables that are joined by relational operators like <, >, =, , ≈, ≤, ≥

A simple statement that combines logical operators into compound statements like 

(count > limit) & ((size – offset)) 0) 

Here, the expression executes only when the entire statement is true and non-zero. 

Sometimes in MATLAB, for a while statement, a logical expression doesn’t get fully evaluated in all its parts. For example: 

while (A & B) = 1;

A = B+1;

printf (‘%A’, B);

end

If A = 0 and B =1, here, the expression doesn’t get executed irrespective of the value of B. Therefore, MATLAB doesn’t consider the need to evaluate B for the ‘&’ operator since they need to be mutually true for the function to progress. 

Similarly in the case of 

while (A|B) = 1;

A = B+1;

printf (‘%A’, B);

end

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If A = 1 and B= 0, here, the expression gets executed as soon as A=1, since ‘|’ operator in MATLAB reads the statement true as soon as one variable satisfies the condition. It doesn’t feel the need to evaluate the second variable. 

• You can always end the execution of an infinite loop by pressing Ctrl+C.
• You can have nesting of while statements with each statement followed by the code and its end keyword.

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