%STINT  Approximate stochastic integrals
%
% Ito and Stratonovich integrals of W dW

randn('state',100)                      % set the state of randn
T = 1; N = 500; dt = T/N;

dW = sqrt(dt)*randn(1,N);               % increments
W = cumsum(dW);                         % cumulative sum

ito = sum([0,W(1:end-1)] .* dW)    
strat = sum((0.5*([0,W(1:end-1)]+W) + 0.5*sqrt(dt)*randn(1,N)).*dW) 

itoerr = abs(ito - 0.5*(W(end)^2-T))
straterr = abs(strat - 0.5*W(end)^2)