Using views_pre_render hook one can alter the output of a view
<?php
/**
* Implements hook_views_pre_render().
*/
function jicustom_views_pre_render(&$view) {
if($view->name=='stock_report'){
$results = $view->result;
foreach ($results as $key => $result) {
$collection_name = $result->field_collection_item_field_name;
if($collection_name == 'field_transaction_items_outgoing'){
//Modify output
$results[$key]->field_field_trans_item_quantity[0]['rendered']['#markup'] = -($result->field_field_trans_item_quantity[0]['raw']['value']);
}
}
}
}
?>
--Source
http://knackforge.com/blog/sivaji/how-alter-views-field-output-programmatically
http://drupal.stackexchange.com/questions/71401/how-can-i-filter-a-view-to-show-recent-items-but-only-one-item-per-user/71402#71402