I have a matrix with human features (f1 .. f4)

Name    f1    f2    f3    f4
africa1    18    1    48    23
usa2    48    23    60    23
africa2    17    3    49    25
africa3    20    6    52    30
usa1    55    20    56    25
china1    35    37    55    87
china2    40    33    50    73
[download]

I wanted to query with selected feature (f1 ..f4), and print the best match.

use strict;
use warnings;

my @array = (37,35,59,70); #Are in the same order as in matrix f1 f2 f
+3 f4

for(my $i = 1; $i <= 4; $i++) {
    my %hash; my @allval;
    my $fh=read_fh($ARGV[0]); #Matrix file here
    while(<$fh>) {
        chomp; next if $. ==1; #Ignore header
        my @val = split('\t', $_);
        $hash{$val[0]}=$val[$i];
        push (@allval, $val[$i]);
    }
    close $fh;
#foreach (sort keys %hash) { print "$_ : $hash{$_}\n";}

my @allval_sorted = sort {$a <=> $b} @allval;
my $find =$array[$i-1];
#my $nearest = @{nearest(\@allval_sorted)}[0];
use List::Util 'max'; my $selected = max grep { $find >= $_ } @allval_
+sorted; my $nearest=$selected;

my @keys = grep { $hash{$_} == $nearest } keys %hash;
print "nearest to $find in array is: $nearest  and name is $keys[0]\n"
+;
undef @allval; undef %hash;

sub nearest {
  my ($a) = @_;  
  my $size = @$a;
  return $a if $size == 1;
  my $mid = int(($size-1) / 2);
  my $test = @$a[$mid];  
  return $test <= $find ?
    (abs($test-$find)<abs(@$a[$mid+1]-$find) ? [$test] : 
       $find <= @$a[$mid+1] ? [@$a[$mid+1]] : nearest([@$a[$mid+1 .. $
+size-1]]))
    :
    (abs($test-$find)<abs(@$a[$mid-1]-$find) ? [$test] : 
       $find >= @$a[$mid-1] ? [@$a[$mid-1]] : nearest([@$a[0 .. $mid]]
+));
}

}


#Open and Read a file
sub read_fh {
    my $filename = shift @_;
    my $filehandle;
    if ($filename =~ /gz$/) {
        open $filehandle, "gunzip -dc $filename |" or die $!;
    }
    else {
        open $filehandle, "<$filename" or die $!;
    }
    return $filehandle;
}
[download]

I wrote script and it print followings; It seems nearest function does not work !!!

WITH NEAREST sub
jitendra@jitendra-Aspire-S3-391[test] perl testMAT.pl mat.txt         
+[10:17PM]
nearest to 37 in array is: 35  and name is china1
nearest to 35 in array is: 37  and name is china1
nearest to 59 in array is: 48  and name is africa1
nearest to 70 in array is: 30  and name is africa3

WITH use List::Util 'max' 
jitendra@jitendra-Aspire-S3-391[test] perl testMAT.pl mat.txt         
+[10:19PM]
nearest to 37 in array is: 35  and name is china1
nearest to 35 in array is: 33  and name is china2
nearest to 59 in array is: 56  and name is usa1
nearest to 70 in array is: 30  and name is africa3
[download]

As you can see, I am opening and closing the matrix file four time, which would be really time consuming on long file.

Is there any other SMART way to achieve the best result? Thanks for you time.

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