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COMP5423 Natural Language Processing

Lecture 2: Text Normalization and Representation

Fridayday, 20 January, 2023

Exercise 1:

Segment the character string of “後天我們去北京” with the backward minimum matching approach (MaxLen=4) and a given dictionary {後天, 我們, 去, 北京}. 

Exercise 2:

Consider the document frequencies of the four terms, “car”, “auto”, “insurance” and “best”, in the Reuters collection of 806,791 documents and their term frequencies for 3 documents denoted as Doc1, Doc2 and Doc3 in the following tables.

(a) Compute the tf-idf weights for these four terms and three documents.

(b) What are the TF-IDF weighted vector representations of three documents in terms of the given four terms?