extracting characters from string

gsub("[^_]*_[^_]*_([^_]*).*", "\\1",  "abcd_efgh_XXXXX_12ab3_dfsfd")

So, a way could be:

gsub("(.*)_(.*)_(.*)_.*", "\\3", ?"abcd_efgh_XXXXX_12ab3_dfsfd")

On Thu, Feb 10, 2011 at 3:47 PM, Soumendra <soumendra at gmail.com> wrote:

Hi Henrique,

I believe your solution is wrong as it is fitted to find 12ab3,
whereas Yan seems to be asking for the characters after the second
underscore and before the third underscore.

For example, gsub(".*_.*_(.*)_.*", "\\1",
"abcd_efgh_XXXXX_12ab3_dfsfd") would still yield 12ab3 even though, as
I understand it, it should have output XXXXX.

I think a straightforward solution would do the job:

strsplit("abcd_efgh_12ab3_dfsfd", "_")[[1]][3]

strsplit("abcd_efgh_XXXXX_12ab3_dfsfd", "_")[[1]][3] has the output
XXXXX, for example.

Of course, I would be wrong if Yan specifically wanted to find the
string 12ab3. But in that case, he would have been asking for matching
(and locating) that substring instead of extracting it.

Regards,

Soumendra


--
Soumendra Prasad Dhanee
Quantitative Analyst, Neural Technologies and Software Pvt. Ltd.

soumendra at neuraltechsoft.com, soumendra at maths.org.in, soumendra at gmail.com
+91-7498076111, +91-8100428686

--
"When you understand why you dismiss all the other possible gods, you
will understand why I dismiss yours." - Stephen Roberts



On 10 February 2011 11:52, Henrique Dallazuanna <wwwhsd at gmail.com> wrote:

Try this:

gsub(".*_.*_(.*)_.*", "\\1", "abcd_efgh_12ab3_dfsfd")

On Thu, Feb 10, 2011 at 9:42 AM, Yan Jiao <y.jiao at ucl.ac.uk> wrote:

Dear R gurus,



If I got a vector with string characters like "abcd_efgh_12ab3_dfsfd",
how could I extract "12ab3", which is the characters after second
underscore and before the third underscore?



Tons of thanks



yan






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