Question

What would be the easiest way to convert a number to base 2 (in a string, as for example 5 would be converted to "0000000000000101") in R? There is intToBits, but it returns a vector of strings rather than a string:

> intToBits(12)
 [1] 00 00 01 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[26] 00 00 00 00 00 00 00

I have tried some other functions, but had no success:

> toString(intToBits(12))
[1] "00, 00, 01, 01, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00, 00"

Answer 1

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 = "")