Reverse digits in R

It is actually the decimial representation of the number that you are testing to be a palindrome, not the number itself (255 is a palendrome in hex and binary, but not decimal).

You can do this fairly simply using pattern matching:

> tmp <- c(100001, 123321, 123456)
> grepl( '^([0-9])([0-9])([0-9])\\3\\2\\1$', tmp )
[1]  TRUE  TRUE FALSE
> 

you could convert the numbers to character, split into individual characters (strsplit), reverse each number (sapply and rev), then paste the values back together (paste) and covert back to numbers (as.numeric). But I think the above is better if you are just interested in 6 digit palendromes.

I don't think rev quite does it. It reverses the elements of the vector, while the question is how to reverse the elements in the vector.

> nums <- sapply(1:10,function(i)as.numeric(paste(sample(1:9,6,TRUE),collapse="")))
> nums
 [1] 912516 568934 693275 835117 155656 378192 343266 685182 298574 666354
> sapply(strsplit(as.character(nums),""), function(i) paste(rev(i),collapse=""))
 [1] "615219" "439865" "572396" "711538" "656551" "291873" "662343" "281586" "475892" "453666"

Edit: I misread the question. Here's my answer for posterity.

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You can use the rev function:

> 1:10
 [1]  1  2  3  4  5  6  7  8  9 10
> rev(1:10)
 [1] 10  9  8  7  6  5  4  3  2  1