v=jarrett(f,x1,x2,tol)

function v=jarrett(f,x1,x2,tol)
% Finds a root of f(x) = 0 using Jarrett's method.
%
% Example call: v=jarrett(f,x1,x2,tol)
% Finds root in range x1 to x2 of the user defined function f using tolerance tol.
gamma=.5; d=1;
while abs(d)>tol
  f2=feval(f,x2); f1=feval(f,x1);
  df=(f2-f1)/(x2-x1); x3=x2-f2/df; d=x2-x3;
  if f1*f2 >0 
    x2=x1; f2=gamma*f1;
  end 
  x2=x3;

end
v=x2;