How to process data from database

monami555monami555 Member Posts: 16 Maven
edited November 2018 in Help

I am just starting with Rapid Miner. In my process I am using the "Process data from Files" component, and now I want to change the data source to database. But I got stuck on this very basic problem: how to process data from database?

I have my connection set and I am able to retrieve data. Here's the smallest example that does not work as I thought it would::

1. I execute a simple query: "select content from document" in Read Database component (the db is Postgresql, and column is type 'character varying')
2. I pass the 'out' result to "Process Documents From Data" component, which has the "create word vector" checkbox checked, and a Tokenize component inside
3. I execute the process
4. In ExampleSet -> Data view I can see the data from db; But the word list is empty

What am I doing wrong here?
How could I debug? My problem is I don't know what kind of data does exactly the "Process Documents From Data" component 'want'.

I am also confused with the "The example set must contain at least one text attribute." error message that is shown for "Process Documents From Data" component - but the same error is present in video tutorials and seem not to be a problem.


  • MariusHelfMariusHelf RapidMiner Certified Expert, Member Posts: 1,869 Unicorn
    Bonjour monami,

    you have to convert the polynominal attributes in the example set generated by the read database operator to a text attribute. The Nominal to Text operator does that for you.

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