Hello I have added this code at Theme functions.php and ir is working fine:

//wpDataTables
add_filter('wpdatatables_filter_cell_val','wpdt_my_hook',10,2);

function wpdt_my_hook($val, $table_id){
if($val == ''){
return 'xxx';
}else{
return $val;
}
}

I need to access and check other column values by row number and column name inside this context. I could not find how to do it. Can you help ? Thx