[Chicago-talk] Combine like hash elements

[richard at rushlogistics.com]

Hello Everybody,
 
Thank you for all the replies. The ID field did not need to be 
preserved. However, I was having difficulty conceptualizing the 
manipulation of the hash so I decided to use DBI->bind_colums instead 
and iterate throught the values in a way that I found at least a bit 
more clear. Still working on cleaning this up but this is at least the 
direction that I am going in. 
 
Thanks again for the help. 
 
   my ($DID, $AMOUNT, $NAME,);
    $sth->bind_columns(\($DID, $AMOUNT, $NAME));

my $lastN;
my $lastA;
my @CAMS;
my $keepN;
my $keepA;

while ($sth->fetch) {
 
if ($lastN) {
   
    if ($NAME eq $lastN) {

    #print "Combine $AMOUNT, $NAME\n";
    $keepA = $AMOUNT + $lastA;
    $keepN = $NAME;
   
    } else {

    $keepA = $AMOUNT;
    $keepN = $NAME;

    }

}

# print "$DID, $AMOUNT, $NAME\n";

$lastN = $NAME;
$lastA = $AMOUNT;

push(@CAMS, $keepA . " " . $keepN);

}

On Mon, 23 Nov 2015 11:28:40 -0600, Steven Lembark  wrote:

       On Mon, 23 Nov 2015 10:10:41 -0600
richard at rushlogistics.com wrote:

> I have a hash reference with the following structure:
>
> {
> '11' => {'AMOUNT' => '20.00','ID' => '11','NAME' => 'Lincoln Park'},
> '12' => {'AMOUNT' => '38.00','ID' => '12','NAME' => 'Bucktown'},
> '13' => {'AMOUNT' => '41.00','ID' => '12','NAME' => 'Lincoln Park'}
> }
>
> Can anyone tell me how I can combine them by 'NAME' so that I would have:
>
> {
> '11' => {'AMOUNT' => '61.00','ID' => '11','NAME' => 'Lincoln Park'},
> '12' => {'AMOUNT' => '38.00','ID' => '12','NAME' => 'Bucktown'},
> }

You don't seem to care about the keys (loosing key "13" wasn't
a problem). 

Q: Are the ID values important or could they be discarded?

If so then just make a new hash keyed by NAME and accumulate
the AMOUNT values:

my %resultz = ();

for( values %inputz )
{
my ( $name, $amt, $id ) = @{ $_ }{ qw( NAME AMOUNT ID ) };
my $val
= $resultz{ $name } ||= { ID => $id, NAME => $name };

$val->{ AMOUNT } += $amt;
}

# at this point %resultz is keyed by name with an id and amount
# for each entry. 

%inputz = ();

while( my ( $name, $val ) = each %resultz )
{
$inputz{ $val->{ ID } } = $val;
}

# at this point the original inputs hash is keyed by ID
# with values having a name, accumulated amount, and id. 
# multiple id's are collapsed into a single ID with the
# value of the first record for that name. 

-- 
Steven Lembark 3646 Flora Pl
Workhorse Computing St Louis, MO 63110
lembark at wrkhors.com +1 888 359 3508
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