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Re: How to calculate a union

  • To: mathgroup at smc.vnet.net
  • Subject: [mg104462] Re: How to calculate a union
  • From: ADL <alberto.dilullo at tiscali.it>
  • Date: Sun, 1 Nov 2009 03:59:57 -0500 (EST)
  • References: <hcgmv6$d16$1@smc.vnet.net>

I do not know why Export seems to behave as you say, but you can
compute in advance the number of terms in each file with this formula:

filelengths = Reverse@CoefficientList[Expand[(x + 1)^n], x]

where the first value (always 1) is for index 0, and so on.
The total Total[filelengths] is of course equal to 2^n.

With this, you might compute in advance the memory required for your
operation and establish when it is too much.

ADL

On Oct 31, 7:54 am, Ramiro <ramiro.barran... at gmail.com> wrote:
> Hi,
>
> I am trying to compute the probability of a union, the formula
> requires to sum and subtract all possible combinations of
> intersections for all pairs, triplets, etc.  When n is big, getting
> all the terms is a challenge.
> ...


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