Narxnet, Error using struct, Conversion to struct from double is not possible.

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In the Matlab UserGuide for Neural Networks Toolbox R2012a (page 3-25), there is an example of a Dynamics Network with the following code:
load magdata
[u,us] = mapminmax(u);
[y,ys] = mapminmax(y);
y = con2seq(y);
u = con2seq(u);
d1 = [1:2];
d2 = [1:2];
narx_net = narxnet(d1,d2,10);
narx_net.divideFcn = '';
narx_net.trainParam.min_grad = 1e-10;
[p,Pi,Ai,t] = preparets(narx_net,u,{},y);
narx_net = train(narx_net,p,t,Pi);
yp = sim(narx_net,p,Pi);
e = cell2mat(yp)-cell2mat(t);
plot(e);
But when I use the code above I get the following error message:
Error using struct Conversion to struct from double is not possible.
However when I use:
narx_net = narxnet(1:2,1:2,10);
Instead of:
d1 = [1:2];
d2 = [1:2];
narx_net = narxnet(d1,d2,10);
The program runs okay.
Then when I try to run the same code but with my own input and output data. So I define u and y myself, I got the same error message again.
Even more strange when I then try to run the original code (see below) then I also get the error message, while previous the code run fine??? When I restart Matlab, the code below works fine again???
load magdata
[u,us] = mapminmax(u);
[y,ys] = mapminmax(y);
y = con2seq(y);
u = con2seq(u);
narx_net = narxnet(1:2,1:2,10);
narx_net.divideFcn = '';
narx_net.trainParam.min_grad = 1e-10;
[p,Pi,Ai,t] = preparets(narx_net,u,{},y);
narx_net = train(narx_net,p,t,Pi);
yp = sim(narx_net,p,Pi);
e = cell2mat(yp)-cell2mat(t);
plot(e);
Hopefully someone can help me with this mystery. Many thanks

Accepted Answer

Sean de Wolski
Sean de Wolski on 10 Aug 2012
If you highlight that selection in the help and right click "Evaluate Selection" do you get the same error?
I am guessing you have a variable/script/function shadowing one of the above since I do not get the error copying what you have above.
  4 Comments
Greg Heath
Greg Heath on 12 Aug 2012
It is best NOT to use the same variable name on both sides of an equation. Try using 3 variables for u and y in
[u,us] = mapminmax(u);
[y,ys] = mapminmax(y);
y = con2seq(y);
u = con2seq(u);

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