Statistics: tracking referrers, page hits, etc.

James, please open a Drupal 8 issue for this concern -> http://drupal.org/project/issues/drupal

That is where something like this would be adressed and not in the docs here.

Hi
Now, we can see every flag statistics by adding the below code in the corresponding files in flag module.
Statistics of Flags.
1. Total no of Flags used
2. Flags & Nodes
3. Flags & Content Types

There 3 steps for getting Flag statistics page in flag module.
STEP 1:
In the file “flag\includes\flag.export.inc”, At line no.251, please append the below code:

/**
* Statistics of Flags.
* 1. Total no of Flags used
* 2. Flags & Nodes
* 3. Flags & Content Types
**/
function flag_stat_form($form, &$form_state) {

$form['flag_settings'] = array(
'#type' => 'fieldset',
'#title' => t('Flag Statistics'),
);
$form['flag_settings']['container1'] = array(
'#type' => 'container',
'#weight' => -10,
);

$form['flag_settings']['container1']['flag_stats'] = array(
'#type' => 'fieldset',
'#title' => t('1. Flag Names and their count'),
'#weight' => -10,
);
$form['flag_settings']['container2']['flag_stats'] = array(
'#type' => 'fieldset',
'#title' => t('2.Nodes & Flags Statistics'),
'#weight' => -10,
);
$form['flag_settings']['container3']['flag_stats'] = array(
'#type' => 'fieldset',
'#title' => t('3. Content types & Flags Statistics'),
'#weight' => -10,
);

// Retrieve a list of all flags, and their count for all users
$result1 = db_query("SELECT flags.name,sum(flag_counts.count) as Count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid GROUP BY flags.name ORDER BY flags.fid ASC")->fetchAll();

// Retrieve a list of all flags, nodes list.
$result2 = db_query("SELECT node.title,flags.fid,flags.name,flag_counts.count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid LEFT JOIN node ON node.nid=flag_counts.content_id UNION SELECT node.title, flags.fid,flags.name,flag_counts.count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid RIGHT JOIN node ON node.nid=flag_counts.content_id")->fetchAll();

// Retrieve a list of all flags, content types list.
$result3 = db_query("SELECT node.title,node_type.type,flags.name,flag_counts.count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid LEFT JOIN node ON node.nid=flag_counts.content_id LEFT JOIN node_type ON node.type=node_type.type UNION SELECT node.title,node_type.type,flags.name,flag_counts.count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid RIGHT JOIN node ON node.nid=flag_counts.content_id LEFT JOIN node_type ON node.type=node_type.type UNION SELECT node.title,node_type.type,flags.name,flag_counts.count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid LEFT JOIN node ON node.nid=flag_counts.content_id RIGHT JOIN node_type ON node.type=node_type.type UNION SELECT node.title,node_type.type,flags.name,flag_counts.count FROM flags LEFT JOIN flag_counts ON flags.fid=flag_counts.fid RIGHT JOIN node ON node.nid=flag_counts.content_id RIGHT JOIN node_type ON node.type=node_type.type")->fetchAll();

// Implementing array of flags, their counts
$flag_count = array();
$flag_list = array();
foreach ($result1 as $row) {
if ($row->Count != '') {
$temp = array('0' => $row->name, '1' => $row->Count);
}
else {
$temp = array('0' => $row->name, '1' => 0);
}
array_push($flag_count,$temp);
array_push($flag_list, $row->name);
}

// Retriving the products list.
$products_list = array();
foreach ($result2 as $row) {
if($row->title != "") {
array_push($products_list,$row->title);
}
}

$products_list = array_values(array_unique($products_list));

// forming a dummy array with zeros.
$final_prod_flags = array_fill(0, count($products_list), array_fill(0, count($flag_list)+1, 0));

// Implementation of second statistics. i.e, Products and Flags relationship.
for($j=0;$jtitle == $products_list[$j]){
if($row->name == $flag_list[$i]){
$final_prod_flags[$j][$i+1] = $row->count;
}// flag if
}//prod if
}// row loop
}//flag for loop
}//prod for loop

// Retriving the content types list.
$content_type_list = array();
foreach ($result3 as $row) {
if($row->type != "") {
array_push($content_type_list,$row->type);
}
}

$content_type_list = array_values(array_unique($content_type_list));

// forming a dummy array with zeros for content type & flag statitics
$final_content_types_flags = array_fill(0, count($content_type_list), array_fill(0, count($flag_list)+1, 0));

// Implementation of third statistics. i.e, content type and Flags relationship.
for($j=0;$jtype == $content_type_list[$j]){
if($row->name == $flag_list[$i]) {
$count = $count + ($row->count);
$final_content_types_flags[$j][$i+1] = $count;
}// flag if
}//prod if
}// row loop
}//flag for loop
}//prod for loop

// Flag-Count Statistics table
$header1 = array(t('Flag name'));
$header1 = array_merge($header1, array(t('Flag count')));

// Node-Flags Statistics table
$header2 = array(t('Product name'));
$header2 = array_merge($header2, $flag_list);

// Content types-Flags Statistics table
$header3 = array(t('Content type name'));
$header3 = array_merge($header3, $flag_list);

$form['flag_settings']['container1']['flag_stats']['flags'] = array(
'#theme' => 'table',
'#header' => $header1,
'#rows' => $flag_count,
'#empty' => t('No content available.'),
);

$form['flag_settings']['container2']['flag_stats']['flags'] = array(
'#theme' => 'table',
'#header' => $header2,
'#rows' => $final_prod_flags,
'#empty' => t('No content available.'),
);

$form['flag_settings']['container3']['flag_stats']['flags'] = array(
'#theme' => 'table',
'#header' => $header3,
'#rows' => $final_content_types_flags,
'#empty' => t('No content available.'),
);
return $form;
}

STEP 2:
In the file, “flag\flag.module”, at line no.69, please add below code:

$items[FLAG_ADMIN_PATH . '/stats'] = array(
'title' => 'Stats',
'page callback' => 'drupal_get_form',
'page arguments' => array('flag_stat_form'),
'access arguments' => array('administer flags'),
'file' => 'includes/flag.export.inc',
'type' => MENU_LOCAL_TASK,
'weight' => 4,
);

STEP 3:
Now just clear the cache,

That’s it.
Now Modules > Flags > configure
You can see another tab ”STATS” at the righthand side parallel to “LIST”,“ACTIONS”,“IMPORT”,“EXPORT”.
If you click on it, we can see three flag statistics tables.

First table says, how many flags being used for how many times.
Second table says, how many nodes are flagged for how many time for each flag.
Third table says, how content types with nodes being flagged with each flag.