Code covered by the BSD License

# Modern Pricing Method using Transforms

### Kienitz Wetterau FinModelling (view profile)

25 Jul 2012 (Updated )

COS, CONV, Lewis Option Pricing Methods including Bermudan and American Options.

xstar(ival, cp, a, b, iter, Grid_k, ...
```% This is material illustrating the methods from the book
% Financial Modelling  - Theory, Implementation and Practice with Matlab
% source
% Wiley Finance Series
% ISBN 978-0-470-74489-5
%
% Date: 02.05.2012
%
% Authors:  Joerg Kienitz
%           Daniel Wetterau
%
% kienitzwetterau_FinModelling@gmx.de
%
% (C) Joerg Kienitz, Daniel Wetterau
%
% Since this piece of code is distributed via the mathworks file-exchange
% it is covered by the BSD license
%
% This code is being provided solely for information and general
% illustrative purposes. The authors will not be responsible for the
% consequences of reliance upon using the code or for numbers produced
% from using the code.

function result = xstar(ival, cp, a, b, iter, Grid_k, ...
model, V, t, r, q, strike, varargin)

cfvals = exp(feval(@CF, model, Grid_k.*pi ./ (b-a), t,r,q,varargin{:}));

x = ival;

eps = 1e-6;

for n = 1:iter
exp_t = exp( 1i .* Grid_k .* pi .* (x - a) ./ (b - a) );
vec = real( cfvals .* exp_t ) .* V;
vec(1) = 0.5*vec(1);

g = (exp(-r * t) * sum(vec, 1)) ...
- cp .* strike .* (exp(x) - 1);

vec = imag(cfvals .* Grid_k .* exp_t) .* V;
vec(1) = 0.5*vec(1);

dg = - exp(-r * t) .* pi / (b - a) .* sum(vec, 1) - cp .* strike .* exp(x);

x = x - (g / dg);
if abs(g) < eps
break;
end
end

result = x;

end```