How to Create a Term Document Matrix

When you want to do analysis on keywords present in text data, you may want to create a term document matrix which creates binary data mapping keywords to each respondent in your data set. This article describes how to convert raw text verbatims:

To a term document matrix represents the words in the text as a table (or matrix) of numbers:

Requirements

A verbatim text variable that contains sentences or phrases. Text variables are represented by an A next to the variable in the Data Sources tree:

Method

1. From the Report tree or toolbar (if working on a Page) select + > Advanced Analysis > Text Analysis > Advanced > Setup Text Analysis.
2. From Properties , select the text variable in the Data > Text Analysis Options > Text variable drop-down or drag the text variable from your Data Sources tree into the Text variable field.
3. Make any modifications to the options in your text analysis setup as described in How to Extract Keywords and Phrases from Text.
4. From the Report tree select + > Advanced Analysis > Text Analysis > Advanced > Term Document Matrix.
5. From Properties > Data > Setup item, select your text analysis output that was created in Steps 3-4.
6. OPTIONAL: Update Minimum document count as needed based on your text analysis.
7. Go to Calculation > Custom code from the toolbar.
8. Click on the page to create the output.
9. Paste the following code into the Code panel:

library(tm)
non.sparse.matrix <- as.matrix(term.document.matrix)

In the code above, replace term.document.matrix with the name of the output that was created in step 6. You can find this by selecting the object and going to Properties > General > General > Name.

Next

How to Create a Sparse Matrix

How to Extract Keywords and Phrases from Text

How to Hook Up a Term Document Matrix or Sparse Matrix to Custom R Code