Analytical Approximation of American Put option derived by G. BARONE-ADESI and R. E. WHALEY 1987.

This computes an approximation of American Put option value and can plot it against asset's price

Efficient Analytical Approximation of American Option Values G. BARONE-ADESI and R. E. WHALEY 1987.

This code computes the Put option approximation derived in the above paper. A critical share price value S_SS is computed and is an output together with put value and the corresponding asset's price. The Put value for S<S_SS is E-S where when S>S_SS American_Put=European_Put+EE ( EE is Early Exercise premium). This model approximate the Early Exercise premium which follows the Black-Scholes partial differential equation.