I am learning the book "Elements of Statistical Learning," but it is very hard because it requires very heavy knowledge about statistics, which I have some, but apparently not enough to understand the derivations in the book. For example,
this is the derivation for the expected prediction error for the linear model Y=beta*X + epsilon. I don't understand it at all! This is very frustrating, and I would really loved to be able to understand this book. Can you tell me some resources using which I can beef up my foundations (whatever it may be) necessary in order to fully comprehend ESL?