1) I first downloaded my document (The Entire Works of Mark Twain) through Project Gutenberg's website as a text document. Save the document in a file on your computer.
2) Open RapidMiner and click "New Process". On the left hand pane of your screen, there should be a tab that says "Operators"- this is where you can search and find all of the operators for RapidMiner and its extensions. By searching the Operators tab for "read", you should get an output like this (you can double click on the images below to enlarge them):
There are multiple read operators depending on which file you have, and most of them work the same way. If you scroll down, there is a "Read Documents" operator. Select this operator and enter it into your Main Process window by dragging it. When you select the Read Documents operator in the Main Process window, you should see a file uploader in the right-hand pane.
4) Now we will move on to processing the document to get a list of its different words and their individual count. Search the Operators list for "Process Documents". Drag this operator the same way as you did for the "Read Documents" operator into the main pane.
Double click the Process Documents operator to get inside the operator. This is where we will link operators together to take the entire text document and split it down into its word components. This consists of several operators that can be chosen by going into the Operator pane and looking at the Text Processing folder. You should see several more folders such as "Tokenization", "Extraction", "Filtering", "Stemming", "Transformation", and "Utility". These are some of the descriptions of what you can do to your document. The first thing that you would want to do to your document is to tokenize it. Tokenization creates a "bag of words" that are contained in your document. This allows you to do further filtering on your document. Search for the "Tokenize" operator and drag it into the "Process Documents" process.
Connect the "doc" node of the process to the "doc" input node of the operator if it has not automatically connected already. Now we are ready to filter the bag of words. In "Filtering" folder under the "Text Processing" operator folder, you can see the various filtering methods that you can apply to your process. For this example, I want to filter certain words out of my document that don't really have any meaning to the document itself (such as the words a, and, the, as, of, etc.); therefore, I will drag the "Filter Stopwords (English)" into my process because my document is in English. Also, I want to filter out any remaining words that are less than three characters. Select "Filter Tokens by Length" and set your parameters as desired (in this case, I want my min number of characters to be 3, and my max number of characters to be an arbitrarily large number since I don't care about an upper bound). Connect the nodes of each subsequent operator accordingly as in the picture.