Column Expression & Rule Nodes Need Access to "Unique Values"

I propose that we add another formula builder option to the Column Exp and Rule node that shows a sorted list of the “Unique Values” for the selected column. Double clicking a value would enter it into the formula just like the other expression building aid tools.

The big flaw to writing formulas in the Column Expression and Rule nodes is that you are forced to do so in a vacuum unable to see or copy and paste from the underlying data. On top of that, you cant even begin leave and return to the configuration dialog of these nodes because an “unfinished” expression throws an error… The lack of access to the column values makes writing long or complex multi-test else if expressions extremely difficult, time consuming and irritating (especially with the safeguard requiring error free expressions prior to an exit of the config window).

The addition of access to the unique values of each column would give us much needed context during expression drafting, reduce error during expression entry, reduce the need to navigate back to KNIME during expression drafting, and highlight data poor data entry problems during cleanup.

I attempt to work around this with a component builds an excel file with a list of sorted unique values and multi-level copy and paste application called “Ditto”, but even with that extreme workaround it would save tons of hours to have these value lists accessible within the nodes themselves.


Hi @iCFO , I certainly agree that the modal nature of configuration dialogs (not just on the “expressions” nodes) can make life difficult because the data is hidden as you are editing the script. On many occasions I’ve had to close the config to go re-look at the specific data that I’m trying to handle.

This is compounded when on some nodes you cannot leave the script in an “unfinished”/error state… So you end up copying it all to clipboard and then deleting it, or commenting it all out, etc.

So yes access to the underlying data, or some snapshot of it, or the ability to leave the script unfinished would be useful to me.

I often resort to taking screenshots of the different data tables so i can refer to those as I edit the config, which works but is frustrating that it has to be that way.

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Hey @takbb,

I love the tip about “commenting everything out” while formula drafting as a way to bypass the inability to save a configuration window in unfinished/error state! Every little trick helps at this point. You are definitely right about more nodes benefitting from this as well. The filter, splitter and Java Snippet nodes come to mind.

I am often working with granular data that has tons of columns, so a screenshot rarely helps on my end. My Excel unique values method allows me to copy and paste Column names / Values / Expressions into the nodes without being forced to navigate away from the Config windows, but it often needs refreshing and has to be opened manually before opening the Config windows… Not user friendly for the masses and requires constant mindfulness.

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I just stumbled on an awesome new KNIME only workaround for copying and pasting values into formulas @takbb!

Use the Interactive Table (Local) node and select “Always on Top” under File. You can attach the table to the prior node and the display window will remain on top and accessible for formula copy & paste into your node configuration windows! It is also sortable on the fly during the process.

It gets even better… You can run / access more than 1 window at once! I have been doing 1 table with only the unique values per column, and a second full table for context. Both are accessible for copy & paste to the configuration window at the same time.

I will see how close I can get to a “unique values” solution that I can just drop in and connect via a macro. I already have a quick temporary macro that drops in the column expression node, jumps back to the prior node, attaches the Interactive Table (Local) node and then changes the setting to always on top, then returns to the Column Expression node configuration window for formula work!

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