While writing error in matrix notation why to put W between
(X.theta-Y)transpose.W.(X.theta-Y)
and why not
W.(X.theta-Y)transpose.(X.theta-Y)
it would be easy to predict the value for any data point. Could have done the calculation for X and Y and then for every data point we could have easily calculated output using W and already calculated value
Locally weighted regression
Hey @srinjoyghosh0702, calculate the shape of each part on pen and paper, and see which combination is possible to be mulitplied. You will get your answer.
Hope this resolved your doubt.
Plz mark the doubt as resolved in my doubts section. 
I hope I’ve cleared your doubt. I ask you to please rate your experience here
Your feedback is very important. It helps us improve our platform and hence provide you
the learning experience you deserve.
On the off chance, you still have some questions or not find the answers satisfactory, you may reopen
the doubt.