[求助]新手求助~（关于初级的神经网络问题） [复制链接]

各位大虾，我在网上看到的教程里的一个程序段，本来想要试试看的： MKzIY:ug  
net=newff([-1 2; 0 5],[3,1],{'tansig','purelin'},'traingd'); P>n}\"z4  
net.trainParam.show = 50; {_T?0L  
net.trainParam.lr = 0.05; 6yH(u}!.  
net.trainParam.epochs = 300; ,7-@eZ  
net.trainParam.goal = 1e-5; D]X&Va  
p = [-1 -1 2 2;0 5 0 5]; YaU)66=u  
t = [-1 -1 1 1]; %ub\+~  
net=train(net,p,t); =kFZ2/P2t(  
TRAINGD, Epoch 0/300, MSE 1.59423/1e-05, Gradient 2.76799/1e-10 }GI8p* ]o=  
TRAINGD, Epoch 50/300, MSE 0.00236382/1e-05, Gradient 0.0495292/1e-10 V|9<*  
TRAINGD, Epoch 100/300, MSE 0.000435947/1e-05, Gradient 0.0161202/1e-10 m%au* 0p  
TRAINGD, Epoch 150/300, MSE 8.68462e-05/1e-05, Gradient 0.00769588/1e-10 <*k]Aa3y  
TRAINGD, Epoch 200/300, MSE 1.45042e-05/1e-05, Gradient 0.00325667/1e-10 !o+[L  
TRAINGD, Epoch 211/300, MSE 9.64816e-06/1e-05, Gradient 0.00266775/1e-10 x.W93e[]H  
TRAINGD, Performance goal met. KYBoGCS>  
a = sim(net,p) {[&$W8Li  
plot(p,t,p,a,'o') s\&qvL1D  
但是为什么老是报错： C]H'z  
??? Input argument "net" is undefined. 0*$?=E