Parameterize pattern match as function argument in R - regex

Question

I've a directory with csv files, about 12k in number, with the naming format being
YYYY-MM-DD<TICK>.csv
. The <TICK> refers to ticker of a stock, e.g. MSFT, GS, QQQ etc. There are total 500 tickers, of various length.
My aim is to merge all the csv for a particular tick and save as a zoo object in individual RData file in a separate directory.
To automate this I've managed to do the csv manipulation, setup as a function which gets a ticker as input, does all the data modification. But I'm stuck in making the file listing stage, passing the pattern to match the ticker being processed. I'm unable to make the pattern to be matched dependent on the ticker.
Below is the function i've tried to make work, doesn't work:
csvlist2zoo <- function(symbol){
csvlist=list.files(path = "D:/dataset/",pattern=paste("'.*?",symbol,".csv'",sep=""),full.names=T)
}
This works, but can't make it work in function
csvlist2zoo <- function(symbol){
csvlist=list.files(path = "D:/dataset/",pattern='.*?"ibm.csv',sep=""),full.names=T)
}
Searched in SO, there are similar questions, not exactly meeting my requirement. But if I missed something please point out in the right direction. Still fighting with regex.
OS: Win8 64bit, R version-3.1.0 (if needed)

Answer 1

Try:
csvlist2zoo <- function(symbol){
list.files(pattern=paste0('\\d{4}-\\d{2}-\\d{2}',symbol, ".csv"))
}
csvlist2zoo("QQQ")
#[1] "2002-12-19QQQ.csv" "2008-01-25QQQ.csv"
csvlist2zoo("GS")
#[1] "2005-05-18GS.csv"
I created some files in the working directory (linux)
v1 <- c("2001-05-17MSFT.csv", "2005-05-18GS.csv", "2002-12-19QQQ.csv", "2008-01-25QQQ.csv")
lapply(v1, function(x) write.csv(1:3, file=x))
Update
Using paste
csvlist2zoo <- function(symbol){
list.files(pattern=paste('\\d{4}-\\d{2}-\\d{2}',symbol, ".csv", sep=""))
}
csvlist2zoo("QQQ")
#[1] "2002-12-19QQQ.csv" "2008-01-25QQQ.csv"