Dollar Cost Averaging reduces variance of returns. Thanks Ben!

dollarcostaveraging.m

ticker = 'USSPX';  % s&p500 index
periods = 1:100; 
nP = numel(periods);
c = yahoo;
dates = {'Jan 1 2000','Sep 6 2014'};
prices = fetch(c,ticker,'Adj Close',dates{1},dates{2}); % should I use Close instead?
nDays = size(prices,1);
nTrials = 50;
returns = zeros(nTrials,nP);
tP = 50*nDays; % total principal invested over time
for t=1:50 % start on different day offsets
    for i=1:nP
        % buy at i-day intervals with available cash accumulated
        buyprices = prices(t:i:end,2);
        available_cash = 50 * i; % 50 dollars a day
        shares = sum(available_cash ./ buyprices); % num shares bought each time
        returns(t,i) = shares * prices(end,2) / tP;
    end
end
plot(1:nP, returns);
ylabel(['returns from ' dates{1} '-' dates{2}]);
xlabel('Dollar Cost Averaging Period (days)');
mR = mean(mean(returns));
fprintf('Average return: %d USD\n', mR);