This node splits the string content of a selected column into logical groups using regular expressions. A capturing group is usually identified by a pair of parentheses, whereby the pattern in such parentheses is a regular expression. Optionally, a group can be named. See Pattern for more information. For each input, the capture groups are the output values. Those can be appended to the table in different ways; by default, every group will correspond to one additional output column.
A short introduction to groups and capturing is given in the Java API . Some examples are given below:
Parsing Patent Numbers
Patent identifiers such as "US5443036-X21" consisting of
a (at most) two-letter country code ("US"), a patent
number ("5443036") and possibly some application code
("X21"), which is separated by a dash or a space
character, can be grouped by the expression
([A-Za-z]{1,2})([0-9]+)[ \-]?(.*$).
Each of the parenthesized terms corresponds to the
aforementioned properties. For named output columns,
we can add group names to the pattern:
(?<CC>[A-Za-z]{1,2})is now identified with "CC" in the output.(?<patentNumber>[0-9]+)is now identified with "patentNumber".[ \-]?is and was never a capturing group so it remains unchanged.(?<applicationCode>.*$)is now identified with "applicationCode".
Strip File URLs
This is particularly useful when this node is used to
parse the file URL of a file reader node (the URL is
exposed as a flow variable and then exported to a table
using a Variable to Table node). The format of such
URLs is similar to "file:c:\some\directory\foo.csv".
Using the pattern
[A-Za-z]*:(.*[/\\])(?<filename>([^\.]*)\.(.*$))
generates four groups: The first group identifies the directory
and is denoted by (.*[/\\]). It consumes all characters
until a final slash or backslash is encountered; in the example,
this refers to "c:\some\directory\". The second group
represents the file name, whereby it encapsulates the
third and fourth group. The third group (([^\.]*))
consumes all characters after the directory,
which are not a dot '.' (which is "foo" in the
above example). The pattern expects a single dot
(final which is ignored) and finally the fourth group (.*$),
which reads until the end of the string and indicates
the file suffix ('csv'). The groups for the above
example are
- Group 1: c:\some\directory
- Group filename: foo.csv
- Group 3: foo
- Group 4: csv
Email Address Extraction
Let's consider a scenario where you have a list of email addresses.
Using the pattern (?<username>.+)@(?<domain>.+),
you can extract the username and domain from the addresses.
The groups for the email address "john.doe@example.com" are:
- Group username: john.doe
- Group domain: example.com
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01_AK_generate_html_from_picturesKNIME Forum- 01_Clickstream_AnalysisKNIME Hub
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Links
- Daten splittenby knimediger on 2020-09-24forum.knime.com/p/103941
- How to split with Regexby armingrudd on 2019-05-19forum.knime.com/p/60767
- Regular expression helpby qqilihq on 2020-04-09forum.knime.com/p/86981
- Regex Coding for Text to Column splittingby danielesser on 2020-11-13forum.knime.com/p/108079
- How do I pull a string given varying input valuesby JanDuo on 2020-07-13forum.knime.com/p/96720
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