Converting decimal to binary in R?

I think that you can use R.utils package, then the intToBin() function

>library(R.utils)

>intToBin(12)
[1] "1100"

> typeof(intToBin(12))
[1] "character"

paste(rev(as.integer(intToBits(12))), collapse="") does the job

paste with the collapse parameter collapses the vector into a string. You have to use rev to get the correct byte order though.

as.integer removes the extra zeros

intToBits is limited to maximum 2^32, but what if we want to convert 1e10 to binary? Here is function for converting float numbers to binary, assuming as they are big integers stored as numeric.

dec2bin <- function(fnum) {
  bin_vect <- rep(0, 1 + floor(log(fnum, 2)))
  while (fnum >= 2) {
    pow <- floor(log(fnum, 2))
    bin_vect[1 + pow] <- 1
    fnum <- fnum - 2^pow
  } # while
  bin_vect[1] <- fnum %% 2
  paste(rev(bin_vect), collapse = "")
} #dec2bin

This function begins to loose digits after 2^53 = 9.007199e15, but works fine for smaller numbers.

microbenchmark(dec2bin(1e10+111))
# Unit: microseconds
#                 expr     min       lq     mean   median      uq    max neval
# dec2bin(1e+10 + 111) 123.417 125.2335 129.0902 126.0415 126.893 285.64   100
dec2bin(9e15)
# [1] "11111111110010111001111001010111110101000000000000000"
dec2bin(9e15 + 1)
# [1] "11111111110010111001111001010111110101000000000000001"
dec2bin(9.1e15 + 1)
# [1] "100000010101000110011011011011011101001100000000000000"

Note that intToBits() returns a 'raw' vector, not a character vector (strings). Note that my answer is a slight extension of @nico's original answer that removes the leading "0" from each bit:

paste(sapply(strsplit(paste(rev(intToBits(12))),""),`[[`,2),collapse="")
[1] "00000000000000000000000000001100"

To break down the steps, for clarity:

# bit pattern for the 32-bit integer '12'
x <- intToBits(12)
# reverse so smallest bit is first (little endian)
x <- rev(x)
# convert to character
x <- as.character(x)
# Extract only the second element (remove leading "0" from each bit)
x <- sapply(strsplit(x, "", fixed = TRUE), `[`, 2)
# Concatenate all bits into one string
x <- paste(x, collapse = "")
x
# [1] "00000000000000000000000000001100"

Or, as @nico showed, we can use as.integer() as a more concise way to remove the leading zero from each bit.

x <- rev(intToBits(12))
x <- paste(as.integer(x), collapse = "")
# [1] "00000000000000000000000000001100"

Just for copy-paste convenience, here's a function version of the above:

dec2bin <- function(x) paste(as.integer(rev(intToBits(x))), collapse = "")