Shell Programming and Scripting

 awk '!/^$/{a[$1]=a[$1]"      "$2} END {for ( i in a) {print i,a[i]}}' filename

awk '!/^$/{var=$2}{getline}{a[$1]=a[$1]"      "(var+$2)/2}END{for ( i in a) {print i,a[i]}}' filename

cat a.txt | paste -d" " - - - - | awk '{print $1" "($2+$4)/2" "($6+$8)/2}'

sub bin{
	my @tmp=@{$_[0]};
	my $result=[];
	for(my $i=0;$i<=($#tmp+1)/2-1;$i++){
		push @{$result}, ($tmp[$i*2]+$tmp[$i*2+1])/2;
	}
	return $result;
}
while(<DATA>){
	my @tmp=split;
	push @{$hash{$tmp[0]}}, $tmp[1];
}
foreach my $key (keys %hash){
	print $key," ";
	my $r_arr=bin($hash{$key});
	print join " ", @{$r_arr};
	print "\n";
}
__DATA__
JR 2
JR 4
NM 5
NM 8
JR 2
NM 2
JR 5
NM 8