How to remove nntraining.setup errors?

a = x4-x5;
y = x1.*x2+x3.*a+log(1+(x6./(x3.*a)));
X = [x1 x2 x3 x4 x5 x6];
n = 1;
net = feedforwardnet(n);
[net, TR] = train(net, X', y');

Error using nntraining.setupPsetupPerWorker (line 62)

Targets T is complex.

Error in nntraining.setup (line 43)

[net,data,tr,err] = setupPerWorker(net,trainFcn,X,Xi,Ai,T,EW,enableConfigure);

Error in network/train (line 335)

[net,data,tr,err] = nntraining.setup(net,net.trainFcn,X,Xi,Ai,T,EW,enableConfigure,isComposite);

Error in GAI_ANN (line 26)

[net, TR] = train(net, X', y')