The Ungroup functionality does not seem to be working. I am using Knime 2.2 on a Mac.
I am able to drag the node onto the protocol, but when i try configure the node, I get the following error:
The dialog cannot be opened for the following reason:
No column in spec compatible to "CollectionDataValue".
Maybe I should have clarified...I am trying to use the Ungroup mode to ungroup the results of the GroupBy node. Is this the intended behavior of the Ungroup?
The node descriptions reads
Creates for each list of collection values a list of rows with the values of the collection in one column and all other columns given from the original row. Rows with an empty collection are skipped, as well as rows that contain only missing values in the collection cell with the 'Skip missing values' option enabled.
So it is not exactly the opposite of the GroupBy node (although the latter can also create collection columns).
Is there any way to perform the opposite of a GroupBy node?
it depends on the aggregation method you used in the groupby node. If you used the collection method for ONE column you can use the ungroup node to reverse the aggregation.
If you use an aggregation method that looses some information about the original data like average, sum, mean their is no node that can restore the original data.