Interest and displaying balance until double the investment?

So I am trying to write a function that will show me a balance after every year with a compound interest of 10% until the balance has reached double the initial investment.

what I have so far is

 x=input('initial investment ');
 b=1;
 for y=x*((1.1)^b)
    if y< 2*y
        b=b+1;
    elseif y >= 2*y
        disp(y);
    end

I'm pretty sure that my issue is trying to get 'b' to increase each year as so far it just stops. I also think I might have to use a while loop but I don't know how.

Answer 1

[Image Analyst]

I don't know what the badly-named "b" is. Try it like this:

initialInvestment = input('Enter initial investment ')
interestRate = input('Enter annual interest rate (0-1)')
currentBalance = initialInvestment;
maxYears = 1000;
for y = 1 : maxYears
  currentBalance = currentBalance * (1 + interestRate);
  fprintf('At the end of year %d, your balance is $%.2f.\n', y, currentBalance);
  if currentBalance >= 2 * initialInvestment
    fprintf('After year %d, your balance has more than doubled!\n', y);
    break;
  end
end

Answer 2

[Roger Stafford]

This is equivalent to evaluating

   y = ceil(log(2)/log(1.1));