How to enable while 1 loop in matlab?

I am planning to make a BMI calculation in which this program will prompt the user to enter new inputs repetitively as long as both inputs are positive. In this case, my input is weight and height. I have applied

while

loop in my code. However, when I enter two positive inputs and after the BMI calculation has been performed, the process ends and exits. May I know which line did I code wrongly?

    while 1
        
        if (Weight > 0 && Height > 0)
            Weight = input('Please Enter Your Weight In kg: ');
            Height = input('Please Enter Your Height In m : ');
            
            BMI = Weight/(Height^2);
            
            if (BMI<=18.5)
                disp(['Health condition: THIN. Your BMI is ', num2str(BMI)]);
                
                
            elseif (BMI>=18.6) && (BMI<=24.9)
                disp(['Health condition: HEALTHY. Your BMI is ', num2str(BMI)]);
                
                
            elseif (BMI<=25) && (BMI<=29.9)
                disp(['Health condition: OVERWEIGHT. Your BMI is ', num2str(BMI)]);
                
                
            else (BMI>=30)
                disp(['Health condition: OBESE. Your BMI is ', num2str(BMI)]);
                
            end
            
            break
        end
    end

[Awais Saeed]

Remove the "break" from the end, it is moving you out of the while loop. For how many times you want to run the loop? Removing the break statement will make the loop run infinitly.

[TEOH CHEE JIN]

Thank you. The suggestion did solve my problem. I wish to loop infinitely.

[Jan]

if (BMI<=18.5)
    ...
elseif (BMI>=18.6) && (BMI<=24.9)    

This fails for a BMI = 18.55. Better:

if (BMI<=18.5)
    ...
elseif (BMI<=24.9)    

The case BMI > 18.5 need not to be checked again, because it was excluded before.

[dpb]

Adding on to @Jan's comment...

The test conditions for the other breakpoints all have similar issue -- there are intervals between each where the breakpoints are written to one decimal but a BMI calculation could return a value between 18.5 and 18.6, etc., for which there would be no output shown.

I see looking at CDC web site that's how they define the intervals and they round to one decimal point, but code to implement the algorithm must handle all possible computed results.

One could alternatively do the calculation, round and then do the switch.

[Dr. Kelsey Joy]

I am glad to read you removed the break based on the previous comment.

I recommend consider putting individual error checks on each of your inputs for Weight and Height variables. You can refer to this example to help with this: https://www.mathworks.com/matlabcentral/fileexchange/102674-educational-validating-user-inputs-numbers-and-strings

Answer 1

[Dr. Kelsey Joy]

I recommend revising your code to remove the break and infinite loop feature. Instead of creating an infinite loop, it may be a better idea to use a run again feature in your code. See sample revision of code below.

Refer to this example for help with error checking (as shown for Weight varaible): https://www.mathworks.com/matlabcentral/fileexchange/102674-educational-validating-user-inputs-numbers-and-strings

run_again = 'yes'; % force start
while strcmpi(run_again,'yes'); % run as long as user wants to keep running
    
        Weight = input('Please Enter Your Weight In kg: ');
        while isempty(Weight) || Weight < 0
            Weight = input('Input a positive value for your weight (kg): ');
        end

        Height = input('Please Enter Your Height In m : ');
        % do an error check like the example for Weight
                
        BMI = Weight/(Height^2);
        
        if BMI<=18.5
            disp(['Health condition: THIN. Your BMI is ', num2str(BMI)]);
            
            
        elseif BMI<=24.9 % BMI>=18.6 is not necessary because anything less than 18.5 will already be filtered out
            disp(['Health condition: HEALTHY. Your BMI is ', num2str(BMI)]);
            
            
        elseif BMI<=29.9 % same as previous: BMI<=25 not necessary
            disp(['Health condition: OVERWEIGHT. Your BMI is ', num2str(BMI)]);
            
            
        else %BMI>=30 % else does not have a condition
            disp(['Health condition: OBESE. Your BMI is ', num2str(BMI)]);
            
        end
        
        run_again = input('Would you like to run this again? (type in "yes" to run again) ','s');
        % error check for yes or no shown in resource cited above
end