Generate an incrementally increasing sequence like 112123123412345

Question

Basically I want to generate a sequence, say:

n is 2, the sequence will be 112
n is 3, sequence is 112123
n is 5, sequence is 112123123412345

I did come up with a solution

n=5
seq=1
for (i in 2:n){
  seq=c(seq,rep(1:n,len=i))
}

I am wondering if there is a way can do it without for loop?

Surfing

Answer 1

Use sequence:

> sequence(1:5)
 [1] 1 1 2 1 2 3 1 2 3 4 1 2 3 4 5

Ecliptic

There is also something somewhat satisfying in doing sequence(sequence(5)) :-) – Bookkeeper

@Chris: make sure to read the "See Also" sections of the help files. ?seq mentions sequence there. – Ecliptic

@JoshuaUlrich Thanks man, I guess I really need to build the habit of reading help page properly, I did go there but ignored everything except arguments and examples. – Surfing

Answer 2

Here is one possibility:

n<-5
unlist(lapply(1:n,function(x) 1:x))
## [1] 1 1 2 1 2 3 1 2 3 4 1 2 3 4 5

Him

more functional, would be unlist(lapply(seq(n),seq)) – Bookkeeper

+1, since sequence is defined as function (nvec) unlist(lapply(nvec, seq_len)). – Ecliptic

Thanks a lot guys! Though this question can be solved by sequence(), it is actually a question from my tutorial practice, asking how to do something using lapply() instead of loop, I think this is what the tutorial question is looking for. – Surfing

if you look at the sequence code you will see how similar are the responses. – Exoenzyme

Answer 3

It'd do something like:

do.call('c', sapply(1:5, seq, from = 1))
# [1] 1 1 2 1 2 3 1 2 3 4 1 2 3 4 5

Pascasia

Answer 4

I misread the question as "how to generate that annoying puzzler sequence," which goes 1,11,21,1112,3112,... :-). So I figured I might as well write a solution to that.

puzseq<-function(seqlen) {
theseq<- list(1)
for( j in 2:seqlen) {

thetab<-table(theseq[[j-1]])
theseq[[j]]<-unlist( sapply( 1:length(thetab), function(k) c(thetab[k], as.numeric(names(thetab)[k])) ))
}
return(theseq)
}

Municipality

This is difficult to read; code formatting is not standard and not consistent. – Snapback

@ClaytonStanley could you clarify what you find unclear? It better be more than lack of indents for loop contents! – Municipality