Reverse digits in R

Question

How can you reverse a string of numbers in R?

for instance, I have a vector of about 1000 six digit numbers, and I would like to know if they are palindromes. I wo

Answer 1

Using intToUtf8 to split, then reverse:

tmp <- c(100001, 123321, 123456)

res <- sapply(tmp, function(i) intToUtf8(rev(utf8ToInt(as.character(i)))))

res
# [1] "100001" "123321" "654321"

To check if it is a palindrome:

tmp == res
# [1]  TRUE  TRUE FALSE

Benchmark

# bigger vector
tmpBIG <- rep(c(100001, 123321, 123456), 4000)

bench::mark(
  GregSnow = { grepl( '^([0-9])([0-9])([0-9])\\3\\2\\1$', tmpBIG) },
  bartektartanus = { tmpBIG == stringi::stri_reverse(tmpBIG) },
  Spacedman = { tmpBIG == sub( '^([0-9])([0-9])([0-9])([0-9])([0-9])([0-9])','\\6\\5\\4\\3\\2\\1', tmpBIG) },
  Joshua = { tmpBIG == sapply(strsplit(as.character(tmpBIG),""), function(i) paste(rev(i),collapse="")) },
  zx8754 = { tmpBIG == sapply(tmpBIG, function(i) intToUtf8(rev(utf8ToInt(as.character(i))))) },
  relative = TRUE)[, 1:9]

# expression         min median `itr/sec` mem_alloc `gc/sec` n_itr  n_gc total_time
#                             
# 1 GregSnow        1      1         6.82      1         NaN    23     0      517ms
# 2 bartektartanus  1.38   1.34      5.02      2.33      NaN    17     0      520ms
# 3 Spacedman       1.58   1.55      4.52      2.33      NaN    15     0      509ms
# 4 Joshua          5.82   5.56      1.24      5.29      Inf     5     6      617ms
# 5 zx8754          6.06   6.17      1         3.98      Inf     4     4      614ms