%BPATH1  Brownian path simulation
fprintf(1,'Desmond J. Higham, An Algorithmic Introduction\n');
fprintf(1,'Numerical Simulation of Stochasitic Differential\n');
fprintf(1,'Equations, SIAM Review, 43(3),2001,525-546\n');
fprintf(1,'Program Bpath1\n');

randn('state',100)           % set the state of randn
T = 1; N = 500; dt = T/N;
dW = zeros(1,N);             % preallocate arrays ...
W = zeros(1,N);              % for efficiency

dW(1) = sqrt(dt)*randn;      % first approximation outside the loop ...
W(1) = dW(1);                % since W(0) = 0 is not allowed
for j = 2:N
   dW(j) = sqrt(dt)*randn;   % general increment
   W(j) = W(j-1) + dW(j); 
end

plot([0:dt:T],[0,W],'r-')    % plot W against t
xlabel('t','FontSize',16) 
ylabel('W(t)','FontSize',16,'Rotation',0)