Re: [R] RegExp question

From: David Winsemius <>
Date: Wed, 16 Jun 2010 12:47:28 -0400

On Jun 16, 2010, at 12:04 PM, Andrej wrote:

> Dear all,
> I'm trying to filter out the "number of leaves" (it should be 1 in the
> example below) from the following string:
>> string
> [1] "Java-Object{J48 pruned tree\n------------------\n: 0 (15.0/3.0)\n
> \nNumber of Leaves : \t1\n\nSize of the tree : \t1\n}"
> Any idea how to do that as simple as possible? Thanks in advance for
> any advice.

?sub # or ?gsub if you need more than one pattern matched (they are on the same page).

This should find the first occurrence of digits following a tab terminated by a line feed and then return only the digits:

string <- "Java-Object{J48 pruned tree\n------------------\n: 0  
(15.0/3.0)\n \nNumber of Leaves : \t1\n\nSize of the tree : \t1\n}" sub("^.+\\t(\\d+)\\n.+$", "\\1", string) [1] "1"

The parens within the search pattern are matched to "\\1". Need to double backslashed within patterns.

> Regards, Andrej


David Winsemius, MD
West Hartford, CT

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Received on Wed 16 Jun 2010 - 16:49:39 GMT

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