download NASDAQ stock data

downloadStockData

# assumes codes are known beforehand
codes <- c("MSFT", "1234")
urls <- paste0("http://www.google.com/finance/historical?q=NASDAQ:",
               codes,"&output=csv")
paths <- paste0(codes,"csv")
missing <- !(paths %in% dir(".", full.name = TRUE))
missing

# simple error handling in case file doesn't exists
downloadFile <- function(url, path, ...) {
      # remove file if exists already
      if(file.exists(path)) file.remove(path)
      # download file
      tryCatch(            
            download.file(url, path, ...), error = function(c) {
                  # remove file if error
                  if(file.exists(path)) file.remove(path)
                  # create error message
                  c$message <- paste(substr(path, 1, 4),"failed")
                  message(c$message)
            }
      )
}
# wrapper of mapply
Map(downloadFile, urls[missing], paths[missing])