Undefined function or variable 'narnet'.

I am trying to predict the future movements on some points but I am quite inexperienced and I get the above error. I am using matlab R2015a. Thanks in advance. Below is my code:

inputDelays = 1:6:19;  % input delay vector
hiddenSizes = [6 3];   % network structure (number of neurons)
net = narnet(inputDelays,hiddenSizes);
[Xs,Xi,Ai,Ts] = preparets(net,{},{},yt);
net = train(net,Xs,Ts,Xi,Ai);
view(net)
net = closeloop(net);
view(net);
yini = yt(end-max(inputDelays)+1:end); % initial values from training data
[Xs,Xi,Ai] = preparets(net,{},{},[yini yv]);
predict = net(Xs,Xi,Ai);
Yv = cell2mat(yv);
Yp = cell2mat(predict);
e = Yv - Yp;
figure(1)
plot(Nu+1:N,Yp,'r')
plot(Nu+1:N,e,'g')
legend('validation data','training data','sampling markers',...
'prediction','error','location','southwest')

Answer 1

[Azzi Abdelmalek]

Check if you have a Neural Network Toolbox

[lori wewe]

Do I necessarily have do download it from their website, can't I do it from matlab, I found this link: http://www.mathworks.com/products/neural-network/

[Azzi Abdelmalek]

If you haven't this toolbox, you need to by it.