vec <- c(1, 0, NA, 1)
new_vec <- c()
for (v in vec) {

    if(!is.na(v) && v == 1) {
      new_vec = c(new_vec, "uno")
    } else if(is.na(v)) {
      new_vec = c(new_vec, NA)
    } else{
      new_vec = c(new_vec, v)
    }
}
print(new_vec)