in reply to Re^4: Restore the original order of an array after sort and performing some funchtion on array values
in thread Restore the original order of an array after sort and performing some funchtion on array values

Hmm. That reads like an exam question. None the less, since it was interesting to code, here's how to do section d):

#! perl -sw use strict; use List::Util qw[ min ]; use Data::Dump qw[ pp ]; my %pvalues = ( 1=> 0.5453980, 2=> 0.4902384, 3=> 0.8167950, 4=> 0.2821822, 5=> 0.4693030, 6=> 0.6491767, 7=> 0.9802138, 8=> 0.1155778, 9=> 0.9585124, 10=> 0.4069490 ); my @orderedKeys = sort { $pvalues{ $b } <=> $pvalues{ $a } } keys %pvalues; my $d = my $n = values %pvalues; $pvalues{ $_ } *= $n / $d-- for @orderedKeys; $pvalues{ $orderedKeys[ $_ ] } = min( @pvalues{ @orderedKeys[ 0 .. $_ ] } ) for 1 .. $n-1; pp \%pvalues; __END__ c:\test>junk68 { 1 => "0.908996666666667", 2 => "0.908996666666667", 3 => "0.9802138", 4 => "0.908996666666667", 5 => "0.908996666666667", 6 => "0.927395285714286", 7 => "0.9802138", 8 => "0.908996666666667", 9 => "0.9802138", 10 => "0.908996666666667", }

I haven't done the last step, (I can't see the stuff in red), so you'll have to work out how to do that yourself. And to do that, you'll first need to understand how the new line above works. And if you can do that, you'll stand some chance of explaining it to whomever is going to check your work.

That'll be $25 :)

BTW:If this is going to be used for real on large volumes of data (which R code often is), then you'll want to replace the use of List::Utilmin() with a custom min() that doesn't use a list for input. Throwing large lists around is a sure-fire way to kill performance. That said, if the lists are large, then all the nested slicing is going to kill you anyway.

For real performance you might consider recoding this for PDL, but that's definitely left as an exercise.


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"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
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Re^6: Restore the original order of an array after sort and performing some funchtion on array values
by sesemin (Beadle) on Mar 04, 2010 at 00:29 UTC
    Thanks a lot. Honestly it is not an exam, I have a larger code in which at some point of it I needed to do this calculation. The algorithm is provided to me by a statistician who was doing it in R but I had to convert it to perl. (Actually you did).

    The red font are the numbers you printed at the end. If any of these >1 then they have to replaced by 1.

    In terms of run time and size of the actual hash varies between 200 to 4000 key/values. I do not think it take a long time to run. Appreciated it again.

      Thanks a lot. Honestly it is not an exam,

      Then all you need to finish the task is a last line of:

      $pvalues{ $_ } = min( $pvalues{ $_ }, 1 ) for keys %pvalues;

      It'd still be a good idea to make sure you understand how the whole code works.


      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.