Fig. 1.

The steps of natural language processing. This figure explains the steps of natural language processing. We turn to keyword extraction to find essential information from a specific document. When these keywords came from different documents, we converted the documents and corresponding keywords into a document-term matrix. The co-occurrence matrix follows the equation. C = A’A, where C is the co-occurrence matrix, A is the document-term matrix, A’ is the transpose of the A matrix, and A’A is the matrix multiplication of A’ and A. They contain a count of the times a given feature occurs in the documents’ relationship with another given feature