we have learned in lectures that in PCA algorithm, the first step is to reduce X by the mean and then divide it by standard variation as seen in lectures:
but it exercise 5 of the assignment the correct form in which I have written and submitted and was correct, we don’t do that:
can anyone help me to understand what I am missing here?
Hi @kvmmn
This thread could offer you some hints and maybe you will come up with an answer. If not, I can try to explain further.
Thanks; it was helpful.
No problem 
But did it answer your question “why”? (since the thread kind of stopped). Did you try, for example, to add ‘Vilnius’ to the words list? What happens in all of the cases (X not changed, X demeaned, or X standardized)?
