R help - Oct 2009 - regular expressions

Dear list,

I have the following text to parse (originating from readLines as some
lines have unequal size),

st = c("START text1 1 text2 2.3", "whatever intermediate
text", "START
text1 23.4 text2 3.1415")

from which I'd like to extract the lines starting with "START",
and
group the subsequent fields in a data.frame in this format:

  text1  text2
     1    2.3
  23.4 3.1415


All the lines containing "START" have the same number of fields, but
this number may vary from file to file.

I have managed to get this minimal example work, but I am at a loss as
for handling an arbitrary number of couples (text value),

library(gsubfn)

( parsed strapply(st, "^START +([[:alnum:]]+) +([0-9.]+) +([[:alnum:]]+)
+([0-9.]+)",c, simplify=rbind,combine=c) )

d = data.frame(parsed[ ,c(2,4)])
names(d) <- apply(parsed[ ,c(1,3)], 2, unique)
d

## this one has more fields: how do I generalize the regular expression?
st2 = c("START text1 1 text2 2.3 text3 5", "whatever intermediate
text", "START text1 23.4 text2 3.1415 text3 6")

Best regards,


Baptiste

Assuming only START fields match pat:
> ## this one has more fields: how do I generalize the regular expression?
> st2 = c("START text1 1 text2 2.3 text3 5", "whatever
intermediate text",
+ "START text1 23.4 text2 3.1415 text3 6")
>
> pat <- "[[:alnum:]]+ +([0-9.]+)"
> s <- strapply(st2, pat, c, simplify = rbind)
>
> pat2 <- "([[:alnum:]]+) +[0-9.]+"
> colnames(s) <- strapply(st2[1], pat2, c, simplify = rbind)
> s
     text1  text2    text3
[1,] "1"    "2.3"    "5"
[2,] "23.4" "3.1415" "6"

If there are non-START fields that do match pat then grep out the
START fields first.

On Mon, Oct 26, 2009 at 9:30 AM, baptiste auguie
<baptiste.auguie at googlemail.com> wrote:
> Dear list,
>
> I have the following text to parse (originating from readLines as some
> lines have unequal size),
>
> st = c("START text1 1 text2 2.3", "whatever intermediate
text", "START
> text1 23.4 text2 3.1415")
>
> from which I'd like to extract the lines starting with
"START", and
> group the subsequent fields in a data.frame in this format:
>
> ?text1 ?text2
> ? ? 1 ? ?2.3
> ?23.4 3.1415
>
>
> All the lines containing "START" have the same number of fields,
but
> this number may vary from file to file.
>
> I have managed to get this minimal example work, but I am at a loss as
> for handling an arbitrary number of couples (text value),
>
> library(gsubfn)
>
> ( parsed > strapply(st, "^START +([[:alnum:]]+) +([0-9.]+)
+([[:alnum:]]+)
> +([0-9.]+)",c, simplify=rbind,combine=c) )
>
> d = data.frame(parsed[ ,c(2,4)])
> names(d) <- apply(parsed[ ,c(1,3)], 2, unique)
> d
>
> ## this one has more fields: how do I generalize the regular expression?
> st2 = c("START text1 1 text2 2.3 text3 5", "whatever
intermediate
> text", "START text1 23.4 text2 3.1415 text3 6")
>
> Best regards,
>
>
> Baptiste
>
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