# In an assignment A(I) = B, the number of elements in B and I must be the same.

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Hi, does anybody know can I fix this error in line "e(i) = d - y2"

for i = 1: size(data_train,2)

x= data_train(:,i);

d = d_train(i); %Pattern mode is selected not Batch mode

% forward propagation

v1 = wh*x; %data entered

y1 = tanh(v1);

y1 = [-1;y1];

v2 = wo*y1;

y2 = (v2); %output and it should be linear active function

% backward propagation:

% adjust output synaptic weights

e(i) = d - y2; %Error calculation

delta_o = e(i) * (1); %bcz deriative of y=x is 1

wo = wo + etha*delta_o* y1'; %set new weight in output layer

% adjust hidden synaptic weights

delta_h = (1-y1.^2) .* (delta_o*wo)';

wh = wh + etha * delta_h(2:end)* x';

end

And in the work space y2 is 3x1 and d is 1x1

### Answers (2)

James Tursa
on 4 Aug 2022

Edited: James Tursa
on 4 Aug 2022

" And in the work space y2 is 3x1 and d is 1x1 "

Then d - y2 will be 3x1. You can't assign a 3-element vector to a 1x1 scalar which is what e(i) is.

If you could show an image of the math you are trying to use we can help you fix up the code.

##### 3 Comments

James Tursa
on 4 Aug 2022

Walter Roberson
on 4 Aug 2022

x= data_train(:,i);

That looks like a column of data, but we cannot tell how large it is

v1 = wh*x; %data entered

If wh is a scalar, then since x is a vector then v1 would be a vector. But we don't know -- wh could be a 2D array and x might be a scalar. v1 is probably a vector, not provably from this code.

y1 = tanh(v1);

same size as v1

y1 = [-1;y1];

That would fail if y1 is not a scalar or a column vector, so given we pass this line, we can figure that v1 is a scalar or vector. Either way, y1 would have to be a column vector after this line.

v2 = wo*y1;

we do not know what the size of wo is, but if it is not a scalar then likely the * operation would fail. So v1 is probably a column vector.

y2 = (v2); %output and it should be linear active function

Same size as v2, probably same size as y1

d = d_train(i); %Pattern mode is selected not Batch mode

scalar

e(i) = d - y2; %Error calculation

Right hand side is scalar minus (likely) column vector. Left hand side names a scalar location. Right hand side does not fit.

If you want to record all of the d-y2 values through the loop, then either assign into columns or else use a cell array.

##### 2 Comments

Walter Roberson
on 4 Aug 2022

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