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  • $\begingroup$ As others have hinted, the more elegant way might be not to use an indexed array, but perhaps we need more information to know why an indexed array is the best solution? $\endgroup$ Commented Jun 22, 2012 at 10:52
  • $\begingroup$ The reasons for using indexed variables as opposed to lists is addressed in the Mathematica reference (reference.wolfram.com/mathematica/tutorial/…). Why should these reasons - sparse definitions made only when needed - not apply when the variable contains an array? $\endgroup$ Commented Jun 22, 2012 at 11:16
  • $\begingroup$ Clearly this is a good question, as it is generating a lot of debate :) Have you found the built in SparseArray doesn't quite fit your application? $\endgroup$ Commented Jun 22, 2012 at 11:44
  • $\begingroup$ As I had written to Szabolcs the reason for choosing an index was the more simple way to change existing code. But the SparseArray is simply the list-solution with better allocation of resources in case of lots of empty cells? I can't see how this is a replacement for an indexed var which essentially allows dynamic programming? $\endgroup$ Commented Jun 22, 2012 at 13:29
  • $\begingroup$ Testing this runs as fast as direct assignment for a non-indexed var. Does this solution have the same memory disadvantages as ReplacePart does? (the indexed-var needs to be copied and reassigned) $\endgroup$ Commented Jun 22, 2012 at 14:53