On 14.11.2011 11:27, Petr PIKAL wrote:
Hi
Thank you. It is a pure magic, something taught in Unseen University.
this is what I got as a help for selecting only letters from set of
character vector.
vzor
[1] "61A" "62C/27" "65A/27" "66C/29" "69A/29" "70C/31"
"73A/31"
[8] "74C/33" "77A/33" "81A/35" "82C/37" "85A/37" "86C/39"
"89A/39"
[15] "90C/41" "93A/41" "94C/43" "97A/43" "98C/45" "101A/45"
"102C/47"
[22] "105A/47" "106C/49" "109A/49" "110C/51" "113A/51"
gsub("[^A-z]", "", vzor)
[1] "A" "C" "A" "C" "A" "C" "A" "C" "A" "A" "C" "A" "C" "A" "C" "A" "C"
[18] "A" "C" "A" "C" "A" "C" "A" "C" "A"
Therefore I expected that
sub("m5.", "\\1", mena) or sub("m5.", "", mena)
selects what I wanted. But it was not the case.
Please can you correct me when I try to evaluate your solution?
gsub(".*_(m5.).*", "\\1", mena)
or
gsub(".*(m5.).*", "\\1", mena)
.* matches any characters
Yes.
() negation? or matching selection for back reference?
The latter. See books about ergular expressions. I think it is also
mentioned in ?regexp and with an example in ?gsub
Finally the expressin matches whole string and evaluates what is matched
by parenthesised value. This evaluation is returned by backreference.
Is it correct evaluation?
Indeed, where \\1 is the first backreference.
Best,
Uwe
Regards
Petr
On 14.11.2011 10:22, Petr PIKAL wrote:
Hi
On 11/14/2011 07:45 PM, Petr PIKAL wrote:
Dear all
I am again (as usual) lost in regular expression use for selection.
Here
are my data:
dput(mena)
c("138516_10g_50ml_50c_250utes1_m53.00-_s1.imp",
"138516_10g_50ml_50c_250utes1_m54.00_s1.imp",
"138516_10g_50ml_50c_250utes1_m55.00_s1.imp",
"138516_10g_50ml_50c_250utes1_m56.00_s1.imp",
"138516_10g_50ml_50c_250utes1_m57.00_s1.imp",
"138516_10g_50ml_50c_250utes1_m58.00_s1.imp",
"138516_10g_50ml_50c_250utes1_m59.00_s1.imp")
I want to select only values "m" foolowed by numbers from 53 to 59.
I used
sub("m5.", "", mena)
which correctly selects those m53 - m59 values but, in contrary to
my
expectation, it replaced the selected values with specified
replacement -
in that case empty string.
What I shall use if I want to get rid of all but m53-m59 from those
strings?
Hi Petr,
How about:
grep("m5",mena)
It gives numeric values which tells me that there is a match in each
string, but as a result I need only
m53-m59 substrings.
gsub(".*_(m5.).*", "\\1", mena)
Uwe Ligges
Regards
Petr
Jim
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