draw a topic h and then draw independent xfrom multinomial distribution
A paper can have several topics, and each topics has different proportions
O is the matrix of topic word, given by the model
h is the topic
2018 10-708 (CMU) Probabilistic Graphical Models {Lecture 25} [Spectral Methods]
原文：https://www.cnblogs.com/ecoflex/p/10281659.html