recur - a bilinear recurrent equation
computes solutions of a bilinear recurrent equation
x(i+1)=-x(i)*(k + sqrt(var)*br(i))
with initial value x0 and driven by a white noise of variance var.
Trajectories are drawn and the empirical Lyapunov exponent is returned ( x(i) is not to much different from exp(y*i) )
A theoretical computation of the Lyapunov exponent is given by
[integr]=logr(k,var)