Convert any R variable's value to string

Question

Coming from Java/Scala, I have been trying to figure out how to convert any value to a string equivalent.

Essentially, I would like to take the output you see in the R REPL and use that as the string.

myFunc <- function(x) { x + 1}
myFunc
#function(x) { x + 1}

Other cases are like with SparkR:

sc
#Java ref type org.apache.spark.api.java.JavaSparkContext id 0

I've tried using options like toString() and as.character(), but those both fail:

toString(myFunc)
#Error in paste(x, collapse = ", ") :
#  cannot coerce type 'closure' to vector of type 'character'

toString(sc)
#Error in as.vector(x, "character") :
#  cannot coerce type 'environment' to vector of type 'character'

I can do a hack like this:

rawString <- function(obj) {
  tmp <- "/tmp/rawString.txt"
  if (file.exists(tmp)) file.remove(tmp)
  sink(tmp)
  print(obj)
  sink()
  dataString <- paste(readLines(tmp))
  if (file.exists(tmp)) file.remove(tmp)
  trimws(dataString)
}
function(obj) {
  tmp <- "/tmp/rawString.txt"
  if (file.exists(tmp)) file.remove(tmp)
  sink(tmp)
  print(obj)
  sink()
  dataString <- paste(readLines(tmp))
  if (file.exists(tmp)) file.remove(tmp)
  trimws(dataString)
}


rawString(sc)
#[1] "Java ref type org.apache.spark.api.java.JavaSparkContext id 0"

rawString(myFunc)
#[1] "function(x) { x + 1}"

But, I would like to avoid writing to and reading from files and relying on sink(). Is there a way to get a string representation like the REPL prints out?

mathematical.coffee · Accepted Answer · 2015-07-15 04:32:35Z

2

Try capture.output. It's essentially your rawString, but built in.

capture.output(myFunc)
[1] "function(x) { x + 1}"

Unfortunately I can't speak for sparkTable as I don't have it.

You might also consider ?dput, which is a good way to provide something for users to copy-paste into their consoles to recreate your variable, though doesn't convert to string (e.g. dput(iris) --> if I were to copy-paste this into my terminal I'd get exactly what you got).

answered Jul 15, 2015 at 4:32

mathematical.coffee

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