How do you create a categorical variable. It appears as if this type is not supported
Add Domain Calculator and apply to your string valued column. It becomes a categorial variable.
If you have numbers and want KNIME to treat them as Strings, then use the Number to String node, to have them converted into nominal values. The spec, second tab in the out-port view, shows the domain values, which can be re-computed with the Domain Calculator; you can even extract those values with Extract Spec node.
thx. I added one but I did not see any effect for the input string Artist, that is, Artist was still a string after I applied the Domain Calculator. Any help would be appreciated.
After execution it should be ok (maybe worth increasing the default number for possible values if you have a lot of artists).
The categorial/nominal columns are also String type columns, but they have values binded to them. (See the Spec tab and check the Artist column after execution. And try to connect the output the node requiring a categorical value.) I think this is just a human term, for the longer "a String type column with the possible values" what is observable from the programmer perspective. (Maybe the description of Domain Calculator might give this use case with the categorial/nominal terms. Or the nodes requiring categorial input might suggest using Domain Calculator.)