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Re^4: Get random unique lines from file

by Marshall (Canon)
on Aug 20, 2012 at 05:16 UTC ( #988394=note: print w/replies, xml ) Need Help??

in reply to Re^3: Get random unique lines from file
in thread Get random unique lines from file

I don't think that this is the best way...
BrowserUk and I both used the core module: List::Util::shuffle;

He understood the FASTA format better than I did and that is fine given that the format of the OP's question was hard to "decode".

The main point is that is that this core shuffle() function works very well, is very fast (a core function that is implemented in 'C') and who's interface is easy to understand. I recommend using it rather than trying to "roll your own".

Oh, BTW, "Core Function" means that this is available on all Perl systems as part of the language - no "extra module installation" is required. .... Well I don't know exactly about "all", but I figure since Perl 5.6 (for more than decade).

  • Comment on Re^4: Get random unique lines from file

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Re^5: Get random unique lines from file
by roboticus (Chancellor) on Aug 30, 2012 at 14:46 UTC


    I wasn't really worried whether it was the best way or not, nor whether it used modules or not. I was just amused by the technique for getting a single random line from a file with equal probability, and wanted to generalize it so I could use it for multiple lines.

    Unfortunately, I haven't come up with any ideas that don't introduce a bias. (I haven't thought about it really hard for the last few days, but I've given it occasional thought during my daily commutes.)

    I might be able to come up with something if I would sit down and analyze the probabilities, but it's not quite interesting enough to work *that* hard on it! ;^)


    When your only tool is a hammer, all problems look like your thumb.

      Unless you are trying to game the tables in "Lost Wages" or do scientific calculations, this doesn't matter at all.
      Don't worry about it if it doesn't matter.


        I'm not really worried about it--it's just an interesting problem. Most (?all?) of my activity here at PM is just me looking for an interesting diversion. This is just another diversion for me.


        When your only tool is a hammer, all problems look like your thumb.

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