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Re: Is there a faster way?

  • To: mathgroup at
  • Subject: [mg30593] Re: [mg30552] Is there a faster way?
  • From: Tomas Garza <tgarza01 at>
  • Date: Thu, 30 Aug 2001 03:51:42 -0400 (EDT)
  • References: <>
  • Sender: owner-wri-mathgroup at

Looks like a big problem. It would be interesting to know where you find the
slowness: is it in the importing operation, or in the actual calculation? I
guess it is in the import, in which case you might rearrange your data so as
to have a single (or just a few) importing process, even if that leaves you
with a huge array to work with. Another possibility (and I'm just talking
through my hat) would be to have your files in Mathematica format previously
Put (>>) there, so that instead of using Import you use Get (<<), which is
much faster. Unless, of course, these files have to be externally changed
often, in which case I don't know what can be done....

Tomas Garza
Mexico City
----- Original Message -----
From: <Moranresearch at>
To: mathgroup at
Subject: [mg30593] [mg30552] Is there a faster way?

> I have a large list of 40,000 file names = f1, each file name corresponds
> a 360 x 19 matrix of real numbers,I need to run the calculation on each
> and save the answer in a list of results. The method below works but is
> is there a better way? Thank you. John R Moran PhD, MD.
> Table[Map[
>     StandardDeviation, {Table[.01*
>             StandardDeviation[
>               Column[Partition[Drop[Import[f1[[j]], "List"], 1], 19], i]]
>           N, {i, 2, 11}]}], {j, 1, Length[f1]}]

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