in reply to Re: Re: Help with multidimensional sorting on arrays of hashed arrays
in thread Help with multidimensional sorting on arrays of hashed arrays

OK, for those onlookers: After extensive conversation in the chatterbox, Clownburner told me the following:

{name} and {data} arrays map 1:1 onto each other, and the first two elements of the {data} array correspond to input and output rates, while the first two elements of the {name} array correspond to filenames.

Clownburner wants a list of filenames sorted by greatest rates (input or output).

First, get the list of name-value pairs for the first two values of {data} from @alldata

my @names_and_rates = map { [ $_->{name}[0], $_->{data}[0] ], [ $_->{name}[1], $_->{data}[1] ] } @alldata;

Now what you've got is an array, each element of which is an anonymous array consisting of a name -> rate pair. i.e.:

@names_and_rates = ( [ name1, rate1], [name2, rate2], ... );

What you want to do is sort that array by the second element of each anonymous array, i.e.

my @final_list = sort { $b->[1] <=> $a->[1] } @names_and_rates; # $b first for descending order

I think that will get you what you want. You can, of course, combine the two statements into one, e.g.

my @final_list = sort { #sort stuff } map { #map stuff } @alldata;

but I think that might be confusing if you come back to this code later, especially given the farrago of syntax. YMMV, IANAProfessional, etc.

I hope this is right and that it helps.

a nicety : if you want to print out the top n, do this:

print "File\t\tRate\n"; foreach (@final_list[0 .. $n-1] ) { print $_->[0], "\t\t", $_->[1], "\n"; }

Philosophy can be made out of anything. Or less -- Jerry A. Fodor

Replies are listed 'Best First'.
Ooooo so Close...
by Clownburner (Monk) on Mar 13, 2001 at 00:26 UTC
    Ok, we're nearly there.. but I have one mysterious problem I cannot understand:

    I inserted this code:
    my @names_and_rates = map { [ $_->{name}[0], $_->{data}[0] ],[ $_- +>{name}[1], $_->{data}[1] ] } @alldata; @maxref = sort { $b->[1] <=> $a->[1] } @names_and_rates; foreach (@maxref[0 .. 2] ) { print $_->[0], "\t\t", $_->[1]*8, "\n +<BR>"; }
    But got this:
    file      rate
              384434.306056 
              191966.35544 
              122524.077608 
    
    So clearly I'm missing the {name} parameter. So, I figured what I needed to do was flatten out the @alldata array a bit. I used this:
    Update Fixed a minor typo in the code below...
    my @maxtmp = sort { $b->{data} <=> $a->{data} } @alldata; my @names_and_rates = map { [ $_->{name}, $_->{data}->[0] ],[ $_-> +{name}, $_->{data}->[1] ] } @maxtmp; @maxref = sort { $b->[1] <=> $a->[1] } @names_and_rates; foreach (@maxref[0 .. 2] ) { print $_->[0], "\t\t", $_->[1]*8, "\n +<BR>"; }
    ..And it worked!
    Now I just need to know a more effective way than that first sort to flatten out the array, since the first sort operation (to @maxtmp) is wasted - but I didn't know how to use the map command to do the same thing.

    Any hints?!? Update 2: Thanks to arturo for the simple fix, below:
    my @names_and_rates = map { [ $_->{name}, $_->{data}->[0] ],[ $_-> +{name}, $_->{data}->[1] ] } @alldata; @maxref = sort { $b->[1] <=> $a->[1] } @names_and_rates; #this next bit just prints the top three foreach (@maxref[0 .. 2] ) { print $_->[0], "\t\t", $_->[1]*8, "\n +<BR>"; }

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