[R] Search and extract string function

[AndrewPage]

Hi all,

I'm trying to write a function that will search and extract from a long
character string, but with a twist: I want to use the characters before and
the characters after what I want to extract as reference points.  For
example, say I'm working with data entries that looks like this:

Drink=Coffee:Location=Office:Time=Morning:Market=Flat

Drink=Water:Location=Office:Time=Afternoon:Market=Up

Drink=Water:Location=Gym:Time=Evening:Market=Closed

Drink=Wine:Location=Restaurant:Time=LateEvening:Market=Closed


...

For my function, I'd like to find what's located between "Location=", and
":Time=" in every instance, and extract it, to return something like
"Office, Office, Gym, Restaurant".

In a previous discussion I found
(http://tolstoy.newcastle.edu.au/R/help/05/03/0344.html), someone wrote a
function where you could find and substitute characters in a string, based
on "pre" and "post" variables:

interp <- function(x, e = parent.frame(), pre = "\\$", post = "" ) {
	for(el in ls(e)) {
		tag <- paste(pre, el, post, sep = "") 
		if (length(grep(tag, x))) x <- gsub(tag, eval(parse(text = el), e), x)
		}
	x
}

I'm not sure how to modify it, however, to do what I want it to do.  Any
suggestions?

Thanks in advance,

Andrew
-- 
View this message in context: http://r.789695.n4.nabble.com/Search-and-extract-string-function-tp2290268p2290268.html
Sent from the R help mailing list archive at Nabble.com.