Assigning variable value according to ifelse()

Im trying to assign a value to output from a function where i want to down sample data. The function should iterate over the data set in chunks but in case the iterator k (not shown here) is through with the whole data set the function should return a random chunk.

The problem is when trying to discriminate by checking the indices and assigning a random value the value returned from the ifelse() statement is a single integer.

n = c(1:972) #indices of negative class
chunkSize = 98
start = 1
stop = -97
n = ifelse(stop < 0,
           n[sample( n, chunkSize)],
           n[start:stop]
)

length(n) [1] 1 n [1] 261

The line n = n[sample( n, chunkSize)]works fine without the ifelse()

> length(n)
[1] 98
> n
 [1] 698 129  85 683 563 598 366 876 965 569 900  54 141 734  33  96 736 311 685 202 663 597
[23] 795 625 763 961 624 352 162 753 524 693 229 173 544 493 477 526 367 716 525 732 198 211
[45] 675 413 708 745 669 715 267 639 519 730  18 588 850  99   4 691 560 682 807 566 568 304
[67]  69 798 474 747 684 117 704 258 410 618 381 281 429 399 824 244  31 558 253 135 326 328
[89] 452 228 608  38 216 156 773 446 827 528

I Guess it has to do with the ifelse() but I'm a beginner on R and I've spent way to much time trying to fix this by now.

Can someone point out what's causing this behavior or come up with an alternative solution?

Many thanks!