derivative of the error w.r.t parameters let's assume my function is as simple as
$y = xW + b$
We define an error function as $E = {\frac{(t - y)}{2}}^2$
I wonder if you can help me to write the derivative of the error w.r.t parameters (W and b) and how I can represent the model as a computational graph, and illustrate how automatic differentiation works.

You first need to plug in the equation for $y$ into the error equation like:
\begin{equation}
E = \frac{1}{2}[t - (xW + b)]^2
\end{equation}
then get the partial derivatives $\frac{\partial E}{\partial x}$ and $\frac{\partial E}{\partial b}$
