Creating table rows, inside a loop?

KNIME Analytics Platform
1

I’d like to learn a general method for creating table rows, inside a loop. I created a simple loop:

  • Originates with a table created via “Table Creator” node.
  • Enters the loop, with “Counting Loop Start” and “Loop End” nodes bounding the loop.
  • Inside the loop, has one node: “Add Empty Rows”, set to add 1 additional row

I’m wondering why the result of running the loop (1000 times) only results in ONE additional row created, rather than 1,000?

2

I tried making a simple workflow based on your approach and came up with this. There’s a clunky Rule-based Row Filter node at the end, but it works. Maybe you can come up with something better?

2018-12-11%2012_59_49-KNIME%20Analytics%20Platform

TableRowAppendLoopExample.knwf (13.2 KB)

3

Perfect; thanks SO much!!!

Now I need to look back at my original workflow, and see what I did wrong… :slight_smile:

4

OK, the difference was that I didn’t have a node after the “Loop End”. When I placed a node (“Rule-based Row Filter”) after the “Loop End” node, my original workflow worked too.

I had “ass-u-med” that after running, with no node after the “Loop End”, I could look at the result of the “Add Empty Rows” node, and see all the rows. I don’t really understand why I can only see the result in a node after “Loop End”, but I can accept that I’m still (very) new to KNIME, and that is just how KNIME works!

Thanks again!!

1 Like
5

You can use Cross Joiner for this task instead of a loop. The said node will produce a Cartesian product between two tables.

The question is of course why you don’t simply use the Add Empty Rows node controlled manually or via a flow variable.