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Extract Information Using Regular Expressions
Contributor I
Hello,
I am following a tutorial from VancouverData on web crawling using RapidMiner.
1. Use CrawlWeb to load listings from Craigslist.org
2. Use ProcessDocumentsFromFiles + Extract Information to create specific item fields
This is all working when I use XPath as the Extract Information query type. However, when I change the query type to Regular Expression, I get errors.
Extract Information Settings:
query type: Regular Expression
attribute type: Nominal
regular expression queries (1):
attribute name: price
query expression: \$\d*
The error coming back is immediate: "Process failed. No group 1"
Any ideas on what I'm doing wrong here?
I am following a tutorial from VancouverData on web crawling using RapidMiner.
1. Use CrawlWeb to load listings from Craigslist.org
2. Use ProcessDocumentsFromFiles + Extract Information to create specific item fields
This is all working when I use XPath as the Extract Information query type. However, when I change the query type to Regular Expression, I get errors.
Extract Information Settings:
query type: Regular Expression
attribute type: Nominal
regular expression queries (1):
attribute name: price
query expression: \$\d*
The error coming back is immediate: "Process failed. No group 1"
Any ideas on what I'm doing wrong here?
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Answers
Use surrounding brackets: (\$\d*) that should fix it. The Error is not helpful at all... ::)