File Reader behavior - Doesn't seem to fully recognize Col0

I'm reading in a csv file using the File Reader node but I'm having some problems. The file reader does appear to read in my Col0 (string) when looking at it in the the table preview. But when I switch to the Specs tab there are no values listed for Col0; the other columns list the values correctly. This is also causing problems in some of the other nodes such as the nominal row filter because it will not recognize Col0 for target column selection (it doesn't appear).

Any ideas what could be wrong? Thanks. Jon Timko.

UPDATE: I was able to work around by adding a domain entry for Col0. Then the other values show up in the spec and all is well. But I don't understand why Col0 didn't show up in the first place

Hi Jon,

I am not quite sure if I got your problem right.

I assume the data is read in correctly, but the list of values in the spec is empty for Col0.

This happens, if the column contains more than 60 different values. In this case KNIME assumes that this is not a column with nominal values and clears the domain. (60 is a fixed magic number in the KNIME platform).

In order to automatically create a domain for a (or multiple) column(s), you can connect the output of the filereader to the "Domain Calculator" node. By default it ignores domains with more than 60 values, but you can change that number in the dialog.

Hope that helps,

 - Peter.


You understood correctly. I was curious about the domain calculator node and I think you've explained it very well. Many thanks. Jon T.