Formatting into text file in R

Question

I have a quick formatting question. I have a set of data in a data frame that looks like this:

Animal   Food   Food ID
 dog     steak   100
 dog     beef    200
 dog     poo     001
 cat     milk    020
 cat     steak   100
 cat     beef    200

which, for programming input purposes, I need to transform into a '.txt' file with a format like this :

<dog>
steak   100
beef    200
poo     001
</dog>

<cat>     
milk    020
steak   100
beef    200
</cat>

Obviously my real data has tens of thousands of entries or else I could do it by hand. Any suggestions would be great. Thanks.

Answer 1

Here's a way:

# create the string
text <- paste0(sapply(unique(dat$Animal), function(x) {
  subdat <- dat[dat$Animal == x, -1]
  subdat[[2]] <- sprintf("%03d", subdat[[2]])
  paste0("<", x, ">\n",
         paste(capture.output(write.table(subdat, sep = "\t",
                                          quote = FALSE, row.names = FALSE, 
                                          col.names = FALSE)), collapse = "\n"),
         "\n</", x, ">")
}), collapse = "\n\n")

# write it to a file
write(text, file = "filename.txt")

The resulting file:

<dog>
steak   100
beef    200
poo 001
</dog>

<cat>
milk    020
steak   100
beef    200
</cat>

The columns are tab-delimited.