Regex split question

[aseeber]

Hi,

I have relatively simple question that I’ve been banging my head on for a while.

I would like to use the Regex Split node to split text like the following:
gH2AX_694;53BP1_159

Ideally, I would like to have search and capture expression that searches for “gH2Axxxx” and “53BP1xxxx” splitting them into two columns.

I know how to do this with cell splitter but I would really like to understand how regex works in Knime. I’ve tried regex101 and the solutions I get there don’t seem to work in Knime.

Does anyone have a suggestion on the best way to go about this?

[qqilihq]

Hi aseeber,

this is a perfect case for the brand new Regex Extractor node in Palladian 2.0 – especially if you’re used to more intuitive tools such as Regex101 you’ll feel right at home. See here for the announcement:

Ka-Boom! Palladian 2.0

Palladian 2.0 for KNIME is here. Since we introduced Palladian into the KNIME ecosystem nine years ago, this is our first major update. It involved tweaking, fixing and improving existing nodes, replacing old nodes with updated ones and adding a new node on which we’d been working for a while and of which we’re particularly proud of: Say hello to Regex Extractor! Regex Extractor Fiddling with data inevitably brings you down to the hell of string voodoo and dark regex magic. If you’re like us a…

You can find an example workflow on NodePit: regex-split-question-20968 — NodePit

Here’s the node configuration for your data:

I used the following regex:

(?<firstValue>gH2A[A-Z0-9_]+);
(?<secondValue>53BP1[A-Z0-9_]+)

It uses the “named capture groups“ firstValue and secondValue which give the name of the output columns. Any way, when editing the expression you’ll always see a preview of the results as you’re used to from Regex101.

Any feedback welcome!

– Philipp

PS: An alternative approach could be to define a “tokenization expression”. This makes sense, if you have a variable number of items separated with a ;

(?:\w+|[^;]+)

It will basically create a match for each value between the semicolon:

[aseeber]

Thanks so much, this is fantastic and just what I was looking for!

I’m testing it out and so far it works perfectly.