Use the 'bit' package to do boolean vector (with NA) with 2-bits per value.

one-bit-boolean.R

library(bit)
library(R6)

#-----------------------------------------------------------------------------
# Outline of an R6 class to wrap a logical vector that may take values: TRUE, FALSE or NA
#
# This uses the 'bit' package for 2-bit booleans (1 bit for t/f and 1bit for NA status)
#
# This uses less memory than a normal logical vector (which uses 32 bits for 
# each logical value)
#
# This reducation in memory will mean that some operations will be much 
# faster as the vector grows. e.g. N = 2^30
#-----------------------------------------------------------------------------
TFNA <- R6::R6Class(
  "TFNA", 
  public = list(
    tf = NULL, 
    na = NULL,
    initialize = function(N, type=c('false', 'random')) {
      type <- match.arg(type)
      t <- system.time({
        if (type == 'false') {
          # initialise to all false with no NAs
          self$tf <- bit::bit(N)
          self$na <- bit::bit(N)
        } else {
          # initialise T, F, NA in approximately 1:1:1 ratio
          self$tf <- as.bit(sample(c(TRUE, FALSE       ), N, replace=TRUE))
          self$na <- as.bit(sample(c(TRUE, FALSE, FALSE), N, replace=TRUE)) 
        }
      })
      
      cat("Initialisation time:", t[['elapsed']], "seconds\n")
    },
    
    get = function(i) {
      if (self$na[i]) {
        NA
      } else {
        self$tf[i]
      }
    },
    
    count = function() {
      t  <- sum(!self$na & self$tf) 
      na <- sum(self$na)
      list(true=t, false=length(self$na)-t-na, na=na)
    },
    
    print = function() {
      print("True/False")
      print(self$tf)
      print("NA status") 
      print(self$na)
    }
  )
)

tfna <- TFNA$new(2^10-1, type='random')
tfna$count()