How to repeat a command until a condition is met?

Here is my part of my code thus far. How would I decrease value of Df until v is approximately 70?

Df=100;
V=exp(-r*T)*min(Df*x_non_us(m+1,:),S_us(m+1,:));
v=mean(V);
while
if abs(v-70)>.1
        Df=Df-.05;
else 
        Df=Df;
end
end
Df

Answer 1

[Jan]

Omit expressions like:

Df = Df;

This is confusing only.

As far as I understand, you want a loop over this piece of the code:

Df = 100;
ready = false;
c  = exp(-r * T);         % Move all repeated expensive
v1 = x_non_us(m + 1, :);  % calculations out of the loop
v2 = S_us(m + 1, :);
iter = 0;
while ~ready
   V = c * min(Df * v1, v2);
   if abs(mean(V) - 70) > 0.1
       Df = Df - 0.05;
   else 
       ready = true;
   end
   
   % Security limit:
   iter = iter + 1;
   if iter > 1e6
      error('Cannot find Df')
   end
end

A binary search between known limits would be more efficient.