WEKA Apriori knode


I am trying to utilize the Apriori knode. My data source is a SQL server.

I get the following error for my data types; ‘Cannot handle string attributes!’

However, when I connect my entire data set, fields that are also string work fine with the knode. They are stored as varchar within our database.

I’ve read that sometimes the knode will run regardless of whether or not it shows an error, however it does not.

Does anybody know what data types this knode accepts? Doesn’t seem to make sense why it would not work.



the weka libary differentiates between two types of ~nominal attributes. They call it a ‘string attribute’ if it has a unspecified number of values and a ‘nominal attribute’ if it has a known set of values (see, e.g., here).

This translates to KNIME to a String column without and with domain-values defined (see the ‘Spec’-tab in the table view). Thus, you can make the node work by applying the Domain Calculator node before (please note that the Domain Calculator by default won’t calculate the domain values if their number exceeds 60 - but that can be increased or disabled in the config dialog).