根据基因位置找最近的基因起始位点

http://www.biotrainee.com/thread-1321-1-1.html

$my_pos=$ARGV[0];

subnearest_search{

    my($array,$value,$low_index,$high_index)=@_;

    $high_index=@{$array}-1 unless$high_index;

    $low_index=0 unless$low_index;

    ## first check whether the arrary is sorted or not !

    if($array->[$low_index] > $array->[$high_index]){

        print"not sort array !!!\n";

        last;

    }

    ## then check

    if($value< $array->[$low_index] ){

        if($value< ($array->[$low_index] + $array->[$low_index-1] )/2){

            return$low_index-1

        }else{

            return$low_index

        }

    }elsif($value> $array->[$high_index]){

         if($value< ($array->[$high_index] + $array->[$high_index-1] )/2){

            return$high_index

        }else{

            return$high_index+1

        }

    }

    $mid_index=int(($low_index+$high_index)/2);

    if($array->[$mid_index] == $value) {

        return$mid_index;

    }

    elsif($array->[$mid_index] < $value) {

        &nearest_search($array,$value,$mid_index+1,$high_index);

    }

    else{

        &nearest_search($array,$value,$low_index,$mid_index-1);

    }

}

openFH,"hg38.tss";

while(){

    chomp;

    @F=split;

    $chr{$F[1]}->{$F[2]}=[($F[0],$F[4])]

}

closeFH;

foreach(keys%chr){

    $sort_pos{$_}=[sort{$a<=>$b}keys%{$chr{$_}}];

}

#print join"\n",@{$sort_pos{'chr1'}}[0..10],'\n';

$nearest_index=&nearest_search($sort_pos{'chr1'},$my_pos);

$nearest_pos=${$sort_pos{'chr1'}}[$nearest_index];

$up_pos=${$sort_pos{'chr1'}}[$nearest_index-1];

$down_pos=${$sort_pos{'chr1'}}[$nearest_index+1];

print"$nearest_index\t$up_pos\t$nearest_pos\t$down_pos\n";