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We can visualize the selected terms for a few topics by creating bar charts out of the c-TF-IDF scores for each topic representation. Insights can be gained from the relative c-TF-IDF scores between and within topics. Moreover, you can easily compare topic representations to each other. To visualize this hierarchy, run the following:


Visualize Term Score Decline

Topics are represented by a number of words starting with the best representative word. Each word is represented by a c-TF-IDF score. The higher the score, the more representative a word to the topic is. Since the topic words are sorted by their c-TF-IDF score, the scores slowly decline with each word that is added. At some point adding words to the topic representation only marginally increases the total c-TF-IDF score and would not be beneficial for its representation.

To visualize this effect, we can plot the c-TF-IDF scores for each topic by the term rank of each word. In other words, the position of the words (term rank), where the words with the highest c-TF-IDF score will have a rank of 1, will be put on the x-axis. Whereas the y-axis will be populated by the c-TF-IDF scores. The result is a visualization that shows you the decline of c-TF-IDF score when adding words to the topic representation. It allows you, using the elbow method, the select the best number of words in a topic.

To visualize the c-TF-IDF score decline, run the following:


To enable the log scale on the y-axis for a better view of individual topics, run the following:


This visualization was heavily inspired by the "Term Probability Decline" visualization found in an analysis by the amazing tmtoolkit. Reference to that specific analysis can be found here.