Assign words to various topics Say I have a document and I want to assign all (or most) of the words to pre-assigned topics. So I could take a random selection of words and manually assign them to the appropriate topics, then I want an algorithm to assign the remaining words to the appropriate topics based on how closely they occur to the manually assigned phrases.

Is there an algorithm or technique that does this? I've looked into topic modelling and word2vec and they seem to assign 'topics' in some arbitrary space without any room for manual training and designation of topics.
Latent Dirichlet allocation (LDA) is a generative statistical model that allows sets of observations to be explained by unobserved groups that explain why some parts of the data are similar. LDA does exactly the same thing you wanted to do.