The Author Online Book Forums are Moving

The Author Online Book Forums will soon redirect to Manning's liveBook and liveVideo. All book forum content will migrate to liveBook's discussion forum and all video forum content will migrate to liveVideo. Log in to liveBook or liveVideo with your Manning credentials to join the discussion!

Thank you for your engagement in the AoF over the years! We look forward to offering you a more enhanced forum experience.

kb0000 (9) [Avatar] Offline
#1
I am confused by the discussion of how to get the matrix factor V. If I highlight just the salient points of the paragraph, the discussion appears to say this:

The last matrix factor, V, ... is the "answer", the topic vector...but we also want to be able to compute it on a new bag of words or TF-IDF vector...we can compute it anew whenever we need it. To create a row in this matrix we multiply the inverse of the V matrix by any new TF-IDF vector...


That is, it appears to say that we do not need to retain the V matrix but can recreate it on demand by...multiplying the inverse of the V matrix by any new vector? If we are trying to calculate the V matrix I'm not sure how exactly we can take its inverse before we calculate it. Undoubtedly this is described in many other resources but this seemed to be a section where you wanted to make the discussion self contained.
hobs (58) [Avatar] Offline
#2
You are right. We didn't do a good job explaining it because I didn't fully understand it at the time. I think it's a little better now.