How can ARIMA model be implemented in matlab 2011a.

How can ARIMA model be implemented in matlab 2011a.I tried to write the code, but am not sure if it is correct.

/*want to model resource demand collected in column 39 of the summaryresourcedemand matrix

y= summaryresourcedemand(:,39);

%*differenced the series once to make it stationary

z=diff(y);

%*training set 1:36000 . p=4 q=2

m = armax(z(1:36000,1),[4,2]);

m.a = conv(m.a,[1 -1]);

%predicting the test set for 5 time ahead values

zp=z(36001:end,1);

yp = predict(m,zp,5);

yp=cell2mat(yp);

%adding to the previous values for obtaining the un-differenced series

pred=(yp)+y(36001:end-1,1);

% Pred is the series predicted by arima . to be compared with original to identify the

%accuracy of results

original=y(36002:end);

Any help would be appreciated . Thanks