Stopping a chart at a certain value.

%For example

%Lets say I made a program for finding radiation decay in a box of some sort. The half life for the radioactive element is every 3 days, and I have to track it until it reaches just before 1/10th of the given safe exposure value of .466.

%So, I simple create and while loop that halves the input, and adds 3 (days) to the output on the chart?

%The example given, with lets say a input value of 150:, It displays:

%Day | Radiation(Status)

%0 150(Unsafe)

%3 75(Unsafe)

%6 37.5(Unsafe)

%9 18.75(Unsafe)

%12 9.375(Unsafe)

%15 4.6875(Unsafe)

%18 2.3438(Unsafe)

%21 1.1719(Unsafe)

%24 0.58594(Unsafe)

%27 0.29297(Safe)

%30 0.14648(Safe)

%33 0.073242(Safe)

%How do I get my code to stop the chart when the radiation level reaches just BEFORE 1/10 of a value (.466) like in this case? My code only displays the ending value, and that is at 36 days, which is incorrect according to this example.

%What I have so far:

% 1. Prompt for Input Data

     x=input('Enter ammount of radiation exposure:');

    y=0;

    while x>(.466/10)*2;
          if x>=(.466/10);
              x=x/2;
              y=y+3;
              a=('Unsafe')
              m=x
              n=y
          end

    end
a=('Safe')

   disp(['Days ', num2str(n), ' Radiation Level = ', num2str(m) ,  num2str(a)])

%Do I need to create some kind of matrix instead to display and track the half life every 3 days?

%Sorry if I am being a bit unclear.

[Walter Roberson]

Note: the "if" statement within the "while" is not doing anything useful in that code. You know the condition is true or else the "while" would have stopped already.

[Ben]

Understood.

Answer 1

[Ben]

Thanks again for the help, I looked back at it and worked out all the kinks, and got it to display correctly now as well. Here is what I was going for:

x=input('Enter ammount of radiation exposure in millirem:');

      y=0;
      while x > (.466/10)*2;
            if x>(.466/10);
                x=x/2';
                y=y+3';
            end 
            if  x>.466;
                a=(' (Unsafe)');
            else x<.466;
                a=(' (Safe)');
            end
  disp(['Day: ', num2str(y), ' Radiation Level= ', num2str(x),  num2str(a)])

end

Answer 2

[Walter Roberson]

Assuming you will be continuing with dividing by 2, change your condition to

while x > (.466/10)*2

[Ben]

Thank you! That solved the issue with it not stopping at the correct value.