> in order to print selected identifiers I'd have to use a loop.
hash/array slices are better than loop, eg:
my $p = random(100);
my %h = map { $_ => 'string'.$_ } 0..99; # for hash lookup
my @a = map 'string'.$_, 0..99; # for array lookup
$, = "\n";
say @h{which($p<0.05)->list}; # hash lookup
say @a[which($p>0.95)->list]; # array lookup
On 07/24/2015 04:50 PM, Marek Gierliński wrote:
> I cannot speak for Kostas, but I often mix text and numbers. Consider an
> example, where I have a list of text identifiers and corresponding numbers,
> e.g., p-values. Now I
> want to find identifiers with p < 0.05. If $id and $p were piddles with text
> identifiers and p-vales, respectively, I could do
>
> my $sel = which($p < 0.05);
> wcols $id($sel);
>
> to print identifiers corresponding to me selection. Alas, I cannot do this,
> so I have to do what Bryan does: employ a hash and an array for converting
> between strings and
> integer ids, and then, in order to print selected identifiers I'd have to use
> a loop. Much less elegant. It would be nice to have (variable-length) strings
> implemented in PDL.
>
> Marek
>
> On Fri, 24 Jul 2015 at 14:25 David Mertens <[email protected]
> <mailto:[email protected]>> wrote:
>
> Hello Kostas,
>
> To follow up on what Bryan said, I wonder what sort of PDL functionality
> you hope to use with a piddle of words, as opposed to a normal Perl array. I
> have a hard time
> imagining you'll need the multidimensional handling PDL provides. Even if
> you want a list of lists, PDL will only work with a collection of lists that
> have identical
> length. A Perl list of lists can accommodate variable length lists, and
> those lists can accommodate strings of variable length. Perl's map and grep
> are pretty flexible
> and fast, too.
>
> One the other hand, if you're doing computational linguistics, the
> typical approach I've seen is to map all words to integers and analyze the
> collections of integers.
> You can build a hash lookup table to map from the words to the integers,
> and a regular Perl array of the words themselves can map integer offsets to
> the original words.
>
> Of course, I could be wrong. What is the actual problem you are trying to
> solve?
>
> David
>
> On Fri, Jul 24, 2015 at 9:10 AM, Bryan Jurish <[email protected]
> <mailto:[email protected]>> wrote:
>
> moin Konstantinos,
>
> afaik, builtin support only includes PDL::Char, which is restricted
> fixed-length strings encoded as byte-values (e.g. ASCII). There's also
> Zakariyya Mughal's
> Data::Frame which seems capable of handling variable-length strings,
> but I'm unclear on the details; perhaps he can chime in. Whenever I need to
> do something like
> this (very often, since I work with text data), I usually end up
> building an extra hash+array pair for mapping back and forth between strings
> and integer-IDs, and
> let PDL work with just the IDs. Not pretty, but it works.
>
> marmosets,
> Bryan
>
> On Fri, Jul 24, 2015 at 2:38 PM, Konstantinos Billis
> <[email protected] <mailto:[email protected]>> wrote:
>
> Hi people,
>
>
> Just a quick question. I am using PDL to build arrays, for
> example "zeroes" function. If I understand correctly, those elements of the
> arrays should contain
> only numbers (or bad, inf etc). Could I use any other function
> for creating strings/words of lists/arrays instead of numbers? In other
> words, for example, to
> initialize an array with NULLs and then add strings or words in
> particular positions of the array.
>
>
> Many Thanks,
> Kostas
>
>
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>
> --
> Bryan Jurish "There is *always* one more
> bug."
> [email protected] <mailto:[email protected]>
> -Lubarsky's Law of Cybernetic Entomology
>
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> --
> "Debugging is twice as hard as writing the code in the first place.
> Therefore, if you write the code as cleverly as possible, you are,
> by definition, not smart enough to debug it." -- Brian Kernighan
>
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> --
> Dr Marek Gierliński
> Data Analyst
> The Data Analysis Group
> The Barton Group
> Division of Computational Biology and GRE
> College of Life Sciences
> University of Dundee, Dundee, Scotland, UK.
> Tel:+44 1382 386427
> www.compbio.dundee.ac.uk/dag.html <http://www.compbio.dundee.ac.uk/dag.html>
>
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