Read in specific, pattern-matched rows from a file

Question

I have a file that is tab-delimited and contains multiple tables each headed by a title, for example "Azuay\n", "Bolivar\n", "Cotopaxi\n", etc, and each table separated by two newlines. Within R, how can I read in this file and select only the table (i.e. specified rows) corresponding to e.g. "Bolivar", while ignoring the table beneath corresponding to "Cotopaxi" and the table above corresponding to "Azuay".

NB. I'd prefer not to modify the table outside R.

The data looks like this. The file is tab-separated.

 Azuay
 region begin       stop
 1A     2017761     148749885
 1A     148863885   150111299
 1A     150329391   150346152
 1A     150432847   247191037


 Bolivar
 region begin           stop 
 2A     2785            242068364
 2A     736640          198339289


 Cotopaxi
 region begin           stop 
 4A     2282            9951846
 4A     11672561        11906166

Answer 1

This seems to do the job:

read.entry.table <- function(file, entry) {

   lines <- readLines(file)

   table.entry <- lines == entry
   if (sum(table.entry) != 1) stop(paste(entry, "not found"))

   empty.lines <- which(lines == "")
   empty.lines <- c(empty.lines, length(lines) + 1L)

   table.start <- which(table.entry) + 1L
   table.end   <- empty.lines[which(empty.lines > table.start)[1]] - 1L

   return(read.table(textConnection(lines[seq(from = table.start,
                                              to   = table.end)]),
                     header = TRUE))
}

read.entry.table("test.txt", "Bolivar")
#   region  begin      stop
# 1     2A   2785 242068364
# 2     2A 736640 198339289

read.entry.table("test.txt", "Cotopaxi")
#   region    begin     stop
# 1     4A     2282  9951846
# 2     4A 11672561 11906166