On Jul 1, 2011, at 11:02 AM, Rainer M Krug wrote:
Hi
I have a question concerning regexp - I want to select with grep all
character strings which contain the numbers 11:20 (code below).
At the moment I am using [], but that obviously does not work, as it
matches
each element in the []. Is there a way to specify that the regexp
should
match 11, but not 1?
Here is the code code:
x <- paste("suff", 1:40, "pref", sep="_")
x
## [1] "suff_1_pref" "suff_2_pref" "suff_3_pref" "suff_4_pref"
"suff_5_pref"
## [6] "suff_6_pref" "suff_7_pref" "suff_8_pref" "suff_9_pref"
"suff_10_pref"
## [11] "suff_11_pref" "suff_12_pref" "suff_13_pref" "suff_14_pref"
"suff_15_pref"
## [16] "suff_16_pref" "suff_17_pref" "suff_18_pref" "suff_19_pref"
"suff_20_pref"
## [21] "suff_21_pref" "suff_22_pref" "suff_23_pref" "suff_24_pref"
"suff_25_pref"
## [26] "suff_26_pref" "suff_27_pref" "suff_28_pref" "suff_29_pref"
"suff_30_pref"
## [31] "suff_31_pref" "suff_32_pref" "suff_33_pref" "suff_34_pref"
"suff_35_pref"
## [36] "suff_36_pref" "suff_37_pref" "suff_38_pref" "suff_39_pref"
"suff_40_pref"
> grep("suff_1[1-9]|suff_20", x, value=TRUE)
[1] "suff_11_pref" "suff_12_pref" "suff_13_pref" "suff_14_pref"
"suff_15_pref" "suff_16_pref"
[7] "suff_17_pref" "suff_18_pref" "suff_19_pref" "suff_20_pref"
i <- paste(11:20, collapse=",")
i
## [1] "11,12,13,14,15,16,17,18,19,20"
That does not look right. You now have a single element with lots of
commas.
grep(paste("suff_[", i, "]", sep=""), x, value=TRUE)
## [1] "suff_1_pref" "suff_2_pref" "suff_3_pref" "suff_4_pref"
"suff_5_pref"
## [6] "suff_6_pref" "suff_7_pref" "suff_8_pref" "suff_9_pref"
"suff_10_pref"
## [11] "suff_11_pref" "suff_12_pref" "suff_13_pref" "suff_14_pref"
"suff_15_pref"
## [16] "suff_16_pref" "suff_17_pref" "suff_18_pref" "suff_19_pref"
"suff_20_pref"
## [21] "suff_21_pref" "suff_22_pref" "suff_23_pref" "suff_24_pref"
"suff_25_pref"
## [26] "suff_26_pref" "suff_27_pref" "suff_28_pref" "suff_29_pref"
"suff_30_pref"
## [31] "suff_31_pref" "suff_32_pref" "suff_33_pref" "suff_34_pref"
"suff_35_pref"
## [36] "suff_36_pref" "suff_37_pref" "suff_38_pref" "suff_39_pref"
"suff_40_pref"
The list of values in an [ ] expression is not delimited by commas.
You are matching on the first letter following the underscore whenever
any character in the "i" string is present (including commas).
> x[40] <- 'suff_,zz_pref'
> grep(paste("suff_[", i, "]", sep=""), x, value=TRUE)
# x[40] matches
## But I would like to have
## [1] "suff_11_pref" "suff_12_pref" "suff_13_pref" "suff_14_pref"
"suff_15_pref"
## [6] "suff_16_pref" "suff_17_pref" "suff_18_pref" "suff_19_pref"
"suff_20_pref"
Version and platform info:
version
_
platform i686-pc-linux-gnu
arch i686
os linux-gnu
system i686, linux-gnu
status
major 2
minor 13.0
year 2011
month 04
day 13
svn rev 55427
language R
version.string R version 2.13.0 (2011-04-13)
sessionInfo()
R version 2.13.0 (2011-04-13)
Platform: i686-pc-linux-gnu (32-bit)
locale:
[1] LC_CTYPE=en_GB.utf8 LC_NUMERIC=C
[3] LC_TIME=en_GB.utf8 LC_COLLATE=en_GB.utf8
[5] LC_MONETARY=C LC_MESSAGES=en_GB.utf8
[7] LC_PAPER=en_GB.utf8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_GB.utf8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] reshape_0.8.4 plyr_1.5.2 tgp_2.4-2 lhs_0.5
[5] RSQLite_0.9-4 DBI_0.2-5 date_1.2-29 simecol_0.7-2
[9] lattice_0.19-26 deSolve_1.10-2
loaded via a namespace (and not attached):
[1] grid_2.13.0 tools_2.13.0
Thanks in advance,
Rainer
--
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology,
UCT), Dipl. Phys. (Germany)
Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa
Tel : +33 - (0)9 53 10 27 44
Cell: +33 - (0)6 85 62 59 98
Fax (F): +33 - (0)9 58 10 27 44
Fax (D): +49 - (0)3 21 21 25 22 44
email: rai...@krugs.de
Skype: RMkrug
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