Text data

Jim's solution is more elegant than the following (and probably more
efficient) but you could also try the following (This let's you sort by
AN/HN, and then by the number at the start of the filename):

text <- c( "26M_AN_C.bmp", "22M_AN_C.bmp", "20M_HA_O.bmp",

"20M_AN_C.bmp", "26M_HA_O.bmp", "22M_HA_O.bmp",
             "31M_AN_C.bmp", "38M_HA_O.bmp")

split <- do.call("rbind",strsplit(text,"_"))

o <- order(split[,2],split[,1],split[,3])

text[o]

[1] 20M_AN_C.bmp" "22M_AN_C.bmp" "26M_AN_C.bmp" "31M_AN_C.bmp"
"20M_HA_O.bmp"
[6] "22M_HA_O.bmp" "26M_HA_O.bmp" "38M_HA_O.bmp"

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Alice Lin
Sent: Wednesday, January 28, 2009 3:38 PM
To: r-help at r-project.org
Subject: [R] Text data


i have a data column of text entries:
26M_AN_C.bmp
22M_AN_C.bmp
20M_HA_O.bmp
20M_AN_C.bmp
26M_HA_O.bmp
22M_HA_O.bmp
31M_AN_C.bmp
38M_HA_O.bmp
.
.
.
.


And I would like to sort by the middle tag: AN, HA, etc.
Is there a way to parse text data in R? 

In excel, I would have used the "left" and "right" function to cut out
just
the middle two letters out and put into another column to sort by. 

Thanks!

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