diff --git a/local/epfl/lib/lib_sel.php b/local/epfl/lib/lib_sel.php
index 5ae3fc3..d3b422f 100755
--- a/local/epfl/lib/lib_sel.php
+++ b/local/epfl/lib/lib_sel.php
@@ -1,206 +1,206 @@
 <?php
 
 class EPFL_LDAP {
 	protected $ldap_host = null;
 	protected $ldap_port = null;
 	protected $ldap_connector = null;
 	protected $ldap_dn = null;
 	protected $ldap_attributes = null;
 
 	protected $ldap_entries = null;
 	protected $formatted_entries = null;
 
 	public function __construct($ldap_host = null, $ldap_port = null) {
 		if (is_null($ldap_host)) $ldap_host = 'ldap.epfl.ch';
 		if (is_null($ldap_port)) $ldap_port = 389;
 		$this->ldap_port = $ldap_port;
 		$this->ldap_host = $ldap_host;
 		$this->ldap_dn = "o=epfl,c=ch";
 		$this->ldap_connector = ldap_connect($ldap_host, $ldap_port) or die("Could not connect to $ldap_host:$ldap_port.");
 		$this->ldap_attributes = array('personaltitle', 'uniqueidentifier', 'mail', 'sn', 'givenname', 'edupersonaffiliation', 'ou', 'title');
 		#$this->ldap_attributes = array('*');
 	}
 
 	protected function find_by_filter($filter, $limit) {
 		$ldap_results = null;
 		$this->ldap_entries = null;
 		$this->formatted_entries = null;
 		$ldap_results = @ldap_search($this->ldap_connector, $this->ldap_dn, $filter, $this->ldap_attributes, 0, $limit);
 		$this->ldap_entries = ldap_get_entries($this->ldap_connector, $ldap_results);
 		$count = $this->ldap_entries['count'];
 		if ($count) {
 			$this->format_entries();
 			return $count;
 		}
 		return false;
 	}
 
 	public function find_by_sciper($sciper, $type = null, $limit = 50) {
 		if (is_null($sciper) or !is_numeric($sciper) or ($sciper < 100000) or ($sciper > 999999))
 			throw new Exception("Invalid sciper: '$sciper'");
 		$filter = 'uniqueIdentifier='.$sciper;
 		if (!is_null($type)) {
 			$filter = "(&($filter)(eduPersonAffiliation=$type))";
 		}
 		return $this->find_by_filter($filter, $limit);
 	}
 
 	public function find_by_givenname($name, $limit = 50) {
 		$filter = 'givenname='.$name;
 		return $this->find_by_filter($filter, $limit);
 	}
 
 	public function find_by_surname($name, $limit = 50) {
 		$filter = 'sn='.$name;
 		return $this->find_by_filter($filter, $limit);
 	}
 
 	public function find_by_ldap_filter($filter, $limit = 50) {
 		return $this->find_by_filter($filter, $limit);
 	}
 
 	protected function format_entries() {
 		$this->formatted_entries = array();
 
 		foreach ($this->ldap_entries as $entry) {
 			if (! is_array($entry)) continue;
 			$formatted_entry = array( 'found' => 1 );
 
 			# Sex
 			switch ($entry['personaltitle'][0]) {
 				case 'Madame':
-					$formatted_entry['sex'] = 'F';
+					$formatted_entry['gender'] = 'F';
 					break;
 				case 'Monsieur':
-					$formatted_entry['sex'] = 'M';
+					$formatted_entry['gender'] = 'M';
 					break;
 				default:
-					$formatted_entry['sex'] = 'X';
+					$formatted_entry['gender'] = 'X';
 			}
 
 			# SCIPER
 			$formatted_entry['sciper'] = $entry['uniqueidentifier'][0];
 
 			# email address
 			if (!array_key_exists('mail', $entry)) {
 				$formatted_entry['email'] = $formatted_entry['sciper'].'@epfl.ch';
 			} else {
 				$formatted_entry['email'] = $entry['mail'][0];
 			}
 
 			# Surname
 			$i = null;
 			#if (array_key_exists(2, $entry['sn'])) {
 			#	$i = 2;
 			#} elseif (array_key_exists(0, $entry['sn'])) {
 			#	$i = 0;
 			#}
 			if (array_key_exists(0, $entry['sn'])) {
 				$i = 0;
 			}
 			if (is_null($i)) {
 				$formatted_entry['surname'] = 'X';
 			} else {
 				$formatted_entry['surname'] = $entry['sn'][$i];
 			}
 
 			# Givenname
 			$i = null;
 			if (array_key_exists(0, $entry['givenname'])) {
 				$i = 0;
 			}
 			if (array_key_exists(2, $entry['givenname'])) {
 				$i = 2;
 			} elseif (array_key_exists(0, $entry['givenname'])) {
 				$i = 0;
 			}
 			if (is_null($i)) {
 				$givenname = 'X';
 			} else {
 				$givenname = $entry['givenname'][$i];
 			}
 			if ($formatted_entry['email'] != $formatted_entry['sciper'].'@epfl.ch') {
 				$email_givenname_size = strlen(explode('.', $formatted_entry['email'])[0]);
 			} else {
 				// email address is based on SCIPER... set $email_givenname_size to 1000 to get all surnames.
 				$email_givenname_size = 1000;
 			}
 			$givennames = explode(' ', $givenname);
 
 			$i = 1;
 			$final_givenname = $givennames[0];
 			$max = count($givennames)-1;
 			while ((mb_strlen($final_givenname, 'UTF-8') < $email_givenname_size) and ($i <= $max)) {
 				$final_givenname .= ' '.$givennames[$i];
 				$i++;
 			}
 
 			# if email as a '-', put it back in the given name if missing
 			if (preg_match('/-/', explode('.', $formatted_entry['email'])[0]) and preg_match('/ /', $final_givenname)) {
 				$final_givenname = preg_replace('/ /', '-', $final_givenname);
 			}
 			$formatted_entry['givenname'] = $final_givenname;
 
 
 			$formatted_entry['name'] = $formatted_entry['surname']." ".$formatted_entry['givenname'];
 
 			# Type
 			$formatted_entry['type'] = $entry['edupersonaffiliation'][0];
 
 			# Details
 			switch ($formatted_entry['type']) {
 				case 'student':
 					if (array_key_exists(0, $entry['ou'])) {
 						if (preg_match('/-/', $entry['ou'][0])) {
 							$formatted_entry['section'] = explode('-', $entry['ou'][0])[0];
 							$formatted_entry['cursus'] = explode('-', $entry['ou'][0])[1];
 						} else {
 							$formatted_entry['section'] = $entry['ou'][0];
 							$formatted_entry['cursus'] = 'XX';
 						}
 					} else {
 						$formatted_entry['section'] = 'XXX';
 						$formatted_entry['cursus'] = 'XX';
 					}
 					break;
 				case 'staff':
 					if (array_key_exists('ou', $entry)) {
 						if (array_key_exists(0, $entry['ou'])) $formatted_entry['where'] = $entry['ou'][0];
 						if (array_key_exists(1, $entry['ou'])) $formatted_entry['where_1'] = $entry['ou'][1];
 					}
 					if (array_key_exists('title', $entry)) {
 						if (array_key_exists(0, $entry['title'])) $formatted_entry['title'] = $entry['title'][0];
 						if (array_key_exists(1, $entry['title'])) $formatted_entry['title_1'] = $entry['title'][1];
 					}
 					break;
 			}
 
 			# Add the newly formatted entry
 			$this->formatted_entries[] = $formatted_entry;
 		}
 
 	}
 
 	public function get_entry() {
 		if (!is_null($this->formatted_entries) and array_key_exists(0, $this->formatted_entries))
 			return $this->formatted_entries[0];
 		else
 			return null;
 	}
 
 	public function get_entries() {
 		return $this->formatted_entries;
 	}
 }
 
 
 class Exporter {
 	public function to_bash($array) {
 		if (is_array($array))
 		foreach($array as $key => $value) echo "$key:$value\n";
 	}
 }
 
 
 
 ?>
diff --git a/local/stats/amcstats b/local/stats/amcstats
index 3064310..2933968 100755
--- a/local/stats/amcstats
+++ b/local/stats/amcstats
@@ -1,265 +1,273 @@
 #!/usr/bin/env php
 <?php
 
 require_once(dirname(__FILE__).'/lib/lib_amcstats.php');
 
 // Printing functions
 
 function printDistribution($line_id = null, $stats = null, $percentage = false) {
 	if (is_null($line_id)) $line_id = "N/A";
 	if (is_null($stats)) {
 		echo "\"$line_id\",1,1.25,1.5,1.75,2,2.25,2.5,2.75,3,3.25,3.5,3.75,4,4.25,4.5,4.75,5,5.25,5.5,5.75,6\n";
 	} else {
 		echo "\"$line_id\"";
 		if (!$percentage) {
 			foreach ($stats['distribution'] as $n) echo ",$n";
 		} else {
 			foreach ($stats['distribution_percentage'] as $n) echo ",$n";
 		}
 		echo "\n";
 	}
 }
 
 
 function printAverage($line_id = null, $stats = null) {
 	if (is_null($line_id)) $line_id = "N/A";
 	if (is_null($stats)) {
 		echo "\"$line_id\",\"n\",\"tot\",\"average\",\"stddev\",\"median\"\n";
 	} else {
 		echo "\"$line_id\",\"{$stats['quarter_mark6']['n']}\",\"{$stats['quarter_mark6']['tot']}\",\"{$stats['quarter_mark6']['average']}\",\"{$stats['quarter_mark6']['stddev']}\",\"{$stats['quarter_mark6']['median']}\"\n";
 	}
 }
 
 // End of printing functions
 
 $shortopts = '';
 $shortopts .= 'h';
 
 $longopts = array(
 	'help',
 	'current-dir:',
 	'only-questions:',
 	'inverse-filter',
 	'csv:',
 	'sample:',
 	'external:',
 	'type:',
 	);
 
 $options = getopt($shortopts, $longopts);
 
 if (empty($options) or array_key_exists('h', $options) or array_key_exists('help', $options)) {
 	echo "USAGE: ".basename(__FILE__)." [parameters (see below)]
 
 Calculates stats on AMC export files (with 'AB' ticked boxes).
 
 Parameters:
 
 \tHelp:                      --help [-h]
 \tData selection:            --csv profname1/filename1/points1[,profname2/filename2/points2] OR --current-dir points
 \tSamples to consider:       --sample global[,profs,sections]
-\tStats to calculate:        --type average[,dist,dist_percentage,questions,marks]
+\tStats to calculate:        --type average[,dist,dist_percentage,discrimination,marks]
 \tQuestion filtering:        [--only-questions filename [--inverse-filter]]
 \tUse external calculation:  --external execname
 
 EXAMPLES:
 ";
 
 echo "\n* Help:\n";
 	echo basename(__FILE__)." -h\n";
 	echo basename(__FILE__)." --help\n";
 
 echo "\n* Basic usage:\n";
 	echo basename(__FILE__)." --current-dir 30\n";
 	echo basename(__FILE__)." --current-dir 30 --sample global --type average\n";
 	echo basename(__FILE__)." --csv tournesol/tournesol.csv/30,favre/favre.csv/29 --sample global --type average\n";
 	echo basename(__FILE__)." --csv tournesol/tournesol.csv/30,favre/favre.csv/29 --sample global --type average --only-questions common-questions.txt\n";
 
 echo "\n* Questions filtering: (common-questions.txt format: one question id per line)\n";
 	echo basename(__FILE__)." (...) --only-question common-question.txt\n";
 	echo basename(__FILE__)." (...) --only-question common-question.txt --inverse-filters\n";
 
 echo "\n* Points to mark conversion with an external script/exec:\n";
 	echo basename(__FILE__)." (...) --external convertor.php
 
 Sample PHP script for custom point to mark conversion:
 
 #!/bin/env php
 <?php
 
 # Exam is on 30 points, no negative points
 #   8pt is 1
 #  21pt is 4
 #  30pt is 6
 
 \$points = (float)\$argv[1];
 
 if (\$points<21) {
-        mark = (float)(3/13*\$points-11/13);
+        \$mark = (float)(3/13*\$points-11/13);
 } else {
         \$mark = (float)(2/9*\$points-2/3);
 }
 echo \$mark;
 ?>
 
 Notes:
 - Script has be be executable (chmod +x).
 - INPUT: total points for the student as first parameter (can be negative if negative marking has been used)
 - OUTPUT: non-rounded mark, with '.' as decimal separator
 ";
 	exit;
 }
 
 
 if (!empty($options['current-dir'])) {
 	$total_points = $options['current-dir'];
 	$filename = array();
 	foreach(scandir('./') as $f) if (preg_match('/\.csv$/', $f)) $filename[] = $f;
 	if (count($filename)) {
 		$csv = "";
 		$first = true;
 		foreach($filename as $f) {
 			if (!$first) $csv .= ',';
 			$csv .= ucfirst(preg_replace('/\.csv$/', '', $f));
 			$csv .= "/$f/$total_points";
 			$first = false;
 		}
 	} else {
 		echo "No AMC stat files found in this directory.\n";
 		exit;
 	}
 }
 
 $only_questions = null;
 if (!empty($options['only-questions'])) {
 	$filename = $options['only-questions'];
 	if(!is_file($filename)) {
 		echo "File not found: $filename\n";
 		exit;
 	}
 	$only_questions = file($filename, FILE_IGNORE_NEW_LINES|FILE_SKIP_EMPTY_LINES);
 }
 
 $external = null;
 if (!empty($options['external'])) {
 	$external = $options['external'];
 	if(!is_file($external)) {
 		echo "External script/exec not found: $external\n";
 		exit;
 	}
 }
 
 $inverse_filter = false;
 if (array_key_exists('inverse-filter', $options)) {
 	$inverse_filter = true;
 }
 
 
 if (!empty($options['csv'])) $csv = $options['csv'];
 if (!empty($options['sample'])) $samples = explode(',', $options['sample']); else $samples = array( 'global');
 if (!empty($options['type'])) $types = explode(',', $options['type']); else $types = array( 'average' );
 
 // Create ExamCalcs object
 $Global = new ExamCalcs();
 
 // Load files
 $loaded = array();
 foreach(explode(',', $csv) as $file_info) {
 	$details = explode('/', $file_info);
 	if (count($details) < 3 ) {
 		echo "CSV file list should look like: tournesol/tournesol.csv/30[,favre@favre.csv@29,...]\n";
 		exit;
 	}
 	$name = $details[0];
 	$filename = $details[1];
 	$total = $details[2];
 
 	if(!is_file($filename)) {
 		echo "File not found: $filename\n";
 		exit;
 	}
 
 	if (in_array($filename, $loaded)) {
 		echo "Trying to load $filename a second time...\n";
 		exit;
 	}
 
 	$Global->addFile($name, $filename, $total, $only_questions, $inverse_filter, $external);
 	$loaded[] = $filename;
 }
 
 foreach ($types as $type) {
 
 	// Build samples
 	foreach ($samples as $sample) {
 		// Print header
 		$sample_header = strtoupper($sample);
 		switch ($type) {
 			case 'average':
 				printAverage($sample_header);
 				break;
 			case 'dist':
 			case 'dist_percentage':
 				printDistribution($sample_header);
 				break;
 			case 'marks':
 				break;
 		}
 
 		// Build samples
 		$Samples = array();
 		switch ($sample) {
 			case 'global':
 				$Samples['global'] = new ExamCalcs($Global->getDataSet());
 				break;
 			case 'sections':
 				foreach ($Global->getSections() as $section) {
 					$tmpSample = new ExamCalcs($Global->getDataSet());
 					$tmpSample->filterBySections($section);
 					$Samples[$section] = $tmpSample;
 				}
 				break;
 			case 'profs':
 				foreach ($Global->getTeachers() as $prof) {
 					$tmpSample = new ExamCalcs($Global->getDataSet());
 					$tmpSample->filterByTeachers($prof);
 					$Samples[$prof] = $tmpSample;
 				}
 				break;
 		}
 
 		// Print stats
+		$is_first = true;
 		foreach ($Samples as $name => $S) {
+			if (!$is_first) echo "\n"; else $is_first = false;
 			$stats = $S->getStats();
 			switch ($type) {
 				case 'average':
 					printAverage($name, $stats);
 					break;
 				case 'dist_percentage':
 					printDistribution($name, $stats, true);
 					break;
 				case 'dist':
 					printDistribution($name, $stats);
 					break;
-				case 'questions':
+				case 'discrimination':
 					echo "\"STATS ON QUESTIONS: ".strtoupper($name)."\"\n";
 					try {
 						$S->printStatsOnCommonItems();
 					} catch (Exception $e) {
 						echo "\"Not enough data\"\n";
 					}
 					break;
 				case 'marks':
 					$marks = $S->getMarks();
 					foreach ($marks as $student) {
 						echo implode(';', $student)."\n";
 					}
 					break;
+				case 'questions':
+					$questions = $S->getQuestions();
+					foreach ($questions as $student) {
+						echo implode(';', $student)."\n";
+					}
+					break;
 			}
+
 		}
-		echo "\n";
 	}
 }
 
 exit;
 ?>
diff --git a/local/stats/lib/lib_amcstats.php b/local/stats/lib/lib_amcstats.php
index ea49887..c7e9557 100755
--- a/local/stats/lib/lib_amcstats.php
+++ b/local/stats/lib/lib_amcstats.php
@@ -1,593 +1,629 @@
 <?php
 
 # some functions for array_maps
 function clean_array($string) { return preg_replace('/"/', '', $string); }
 function decimal_conversion($string) { return preg_replace('/,/', '.', $string); }
 function square($n) { return($n*$n); }
 
 # standard deviation function (if PECL stats not available)
 if (!function_exists('stats_standard_deviation')) {
     function stats_standard_deviation(array $a, $sample = false) {
         $n = count($a);
         if ($n === 0) {
             trigger_error("The array has zero elements", E_USER_WARNING);
             return false;
         }
         if ($sample && $n === 1) {
             trigger_error("The array has only 1 element", E_USER_WARNING);
             return false;
         }
         $mean = array_sum($a)/$n;
         $carry = 0.0;
         foreach ($a as $val) {
             $d = ((double) $val) - $mean;
             $carry += $d * $d;
         }
         if ($sample) --$n;
         return sqrt($carry / $n);
     }
 }
 
 class AmcReader {
 	protected $filename = null;
 	protected $teacher = null;
 	protected $raw_data = null;
 	protected $columns = null;
 	protected $students = null;
 	protected $exam_points = null;
 
 	public function __construct($filename, $teacher, $exam_points, $only_questions = null, $inverse_filter = false, $external = null) {
 		if (!file_exists($filename))
 			throw new Exception('File not found: '.$filename);
 		$this->filename = $filename;
 
 		$this->teacher = $teacher;
 		$this->exam_points = $exam_points;
 
 		$raw_data = file($this->filename, FILE_IGNORE_NEW_LINES);
 		$this->raw_data = array();
 		foreach($raw_data as $line) {
 			$line = array_map("clean_array", explode(';', $line));
 			$line =  array_map("decimal_conversion", $line);
 			$this->raw_data[] = $line;
 		}
 		$this->parseHeader();
 		$this->parseStudents($only_questions, $inverse_filter, $external);
 	}
 
 	public function getStudents() {
 		return $this->students;
 	}
 
 	protected function parseHeader() {
 		foreach($this->raw_data[0] as $col_id => $value) {
 			// Analyse header from CSV file, based on content
 			$item = array();
 			switch ($value) {
 				case "ID":
 				case "NAME":
 				case "EMAIL":
 				case "SECTION":
 				case "Mark":
 					$item['name'] = $value;
 					$item['type'] = "info";
 					break;
 				case "SCIPER":
 					$item['name'] = $value;
 					$item['type'] = "unique_id";
 					break;
 				default:
 					$item['name'] = $value;
 					if (preg_match('/^TICKED:/', $value)) {
 						$item['name'] = preg_replace('/^TICKED:/', '', $value);
 						$item['type'] = "ticked";
 					} else {
 						$item['type'] = "question";
 						$item['subtype'] = $this->guessSubtype($col_id);
 					}
 					
 			}
 			// Stats will be computed at a later stage
 			$item['stats'] = null;
 			$this->columns[] = $item;
 		}
 	}
 
 	protected function guessSubtype($col_id) {
 		$subtype = null;
 		$min_points = 0;
 		$max_points = 0;
 		$decimal = false;
 		foreach($this->raw_data as $line) {
 			if (preg_match('/\./', $line[$col_id]))	$decimal = true;
 			if ($line[$col_id] > $max_points) $max_points = $line[$col_id];
 		}
 
 		// This only works for MATHS exams...
 		if ($decimal or $max_points > 3) {
 			// Only open questions have decimal points
 			return 'open';
 		}
 		if ($max_points == 3) return 'mc';
 		if ($max_points == 1) return 'tf';
 
 		return 'unknown';
 	}
 
 	protected function getColIdByName($name) {
 		foreach ($this->columns as $id => $col) if ($col['name'] == $name) return $id;
 		throw new Exception('Column not found: '.$name);
 	}
 
 	protected function getColIdsByType($type, $name = null) {
 		$ids = array();
 		if (is_null($name)) {
 			foreach ($this->columns as $id => $col) if ($col['type'] == $type) $ids[] = $id;
 		} else {
 			foreach ($this->columns as $id => $col) if ($col['type'] == $type and $col['name'] == $name) $ids[] = $id;
 		}
 		if (count($ids) == 0) {
 			if (is_null($name)) throw new Exception('Column type not found: '.$type);
 			throw new Exception('Column type not found: '.$type.'/'.$name);
 		}
 		if (count($ids) == 1) return $ids[0];
 		return $ids;
 	}
 
 	protected function getQuestionNameByColId($id) {
 		if (array_key_exists($id, $this->columns) and $this->columns[$id]['type'] == 'question')
 			return $this->columns[$id]['name'];
 		throw new Exception('Column not found, or is not a question: '.$id);
 	}
 
 	protected function getMaximumPointsByColId($id) {
 		$maximum = 0.0;
 		foreach($this->raw_data as $student) if ((float)$student[$id] > $maximum) $maximum = (float)$student[$id];
 		return $maximum;
 	}
 
 	protected function parseStudents($only_questions, $inverse_filter, $external) {
 		foreach($this->raw_data as $line => $student) {
 			if ($line == 0) continue; // skip header
 
 			$data = array('teacher' => $this->teacher);
 
 			foreach(array('ID', 'SCIPER', 'NAME', 'EMAIL', 'SECTION') as $key) {
 				$data[$key] = $student[$this->getColIdByName($key)];
 			}
 
 			// Get points
 			$points = array();
 			$data['items'] = array();
 			foreach($this->getColIdsByType('question') as $col) {
 				$item = array();
 				$item['name'] = $this->getQuestionNameByColId($col);
 
 				// Should we filter this question ?
 				if (is_null($only_questions)
 					or (!$inverse_filter and in_array($item['name'], $only_questions))
 					or ($inverse_filter and !in_array($item['name'], $only_questions))
 					) {
 					// Take this question into account
 					$item['points'] = (float)$student[$col];
 					$item['max_points'] = $this->getMaximumPointsByColId($col);
 					if ($item['max_points'] == 0) {
 						// Cancelled question ? Count it right for everyone
 						$item['right'] = 1;
 					} else {
 						$item['right'] = max((float)($item['points']/$item['max_points']), 0.0);
 					}
 					$points[] = $item['points'];
 					$item['ticked'] = $student[$this->getColIdsByType('ticked', $item['name'])];
 					$item['type'] = $this->columns[$col]['type'];
 					$item['subtype'] = $this->columns[$col]['subtype'];
 					$data['items'][] = $item;
 				}
 			}
 
 			$data['total'] = array_sum($points);
 
 			$data['present'] = (int)(array_sum(array_map("square", $points))>0);
 
 			$data['exam_points'] = $this->exam_points;
 
 			// Compute marks
 			if ($data['present']) {
 				$data['positive_total'] = (float)max($data['total'], 0.0);
 				if (is_null($external)) {
 					$data['mark6'] = (float)min($data['positive_total']/($this->exam_points)*5.0+1, 6.0);
 				} else {
 					$output = array();
 					exec("./".$external." ".$data['total'], $output);
 					$data['mark6'] = (float)trim($output[0]);
 				}
 				$data['quarter_mark6'] = (float)round($data['mark6']*4.0, 0)/4.0;
 			} else {
 				$data['positive_total'] = 'n/a';
 				$data['mark6'] = 'abs';
 				$data['quarter_mark6'] = 'abs';
 			}
 
 			if (preg_match('/^FAKE/', $data['SCIPER'])) {
 				if ($data['present']) $data['type'] = 'unregistered';
 				else $data['type'] = 'unused';
 			} else $data['type'] = 'student';
 
 			$this->students[] = $data;
 		}
 	}
 }
 
 // Compare students on total (higher to lower)
 function cmp_total($a, $b)
 {
     if ($a['total'] == $b['total']) {
         return 0;
     }
     return ($a['total'] < $b['total']) ? 1 : -1;
 }
 
 class ExamCalcs {
 	protected $dataset = null;
 	protected $tmp_dataset = null;
 
 	public function __construct($dataset = null) {
 		$this->dataset = array();
 		if (!is_null($dataset)) $this->dataset = $dataset;
 	}
 
 	public function addFile($teacher, $teacher_file, $max_points, $only_questions = null, $inverse_filter = false, $external = null) {
 		#echo "Adding $teacher ($teacher_file) to the dataset ($max_points points).\n";
 		$AR = new AmcReader($teacher_file, $teacher, $max_points, $only_questions, $inverse_filter, $external);
 		$this->addDataSet($AR->getStudents());
 	}
 
 	public function addDataSet($data) {
 		foreach ($data as $student) $this->dataset[] = $student;
 	}
 
 	public function filterBySections($sections, $update = true) {
 		$dataset = array();
 		foreach ($this->dataset as $student) {
 			if (is_array($sections)) {
 				if (in_array($student['SECTION'], $sections))
 					$dataset[] = $student;
 			} else {
 				if ($student['SECTION'] == $sections)
 					$dataset[] = $student;
 			}
 		}
 		if ($update) $this->dataset = $dataset;
 		return $dataset;
 	}
 
 	public function filterByTeachers($teachers, $update = true) {
 		$dataset = array();
 		foreach ($this->dataset as $student) {
 			if (is_array($teachers)) {
 				if (in_array($student['teacher'], $teachers))
 					$dataset[] = $student;
 			} else {
 				if ($student['teacher'] == $teachers)
 					$dataset[] = $student;
 			}
 		}
 		if ($update) $this->dataset = $dataset;
 		return $dataset;
 	}
 
 	public function getTeachers() {
 		$teachers = array();
 		foreach ($this->dataset as $student) {
 			if (!in_array($student['teacher'], $teachers)) $teachers[] = $student['teacher'];
 		}
 		return $teachers;
 	}
 
 	public function getSections() {
 		$sections = array();
 		foreach ($this->dataset as $student) {
 			$section = $student['SECTION'];
 			if (!in_array($section, $sections) and $section != 'XXX') $sections[] = $section;
 		}
 		return $sections;
 	}
 
 	public function printStatsOnCommonItems() {
 		// Sort dataset by points
 		$dataset = $this->sortByTotalPoints(false);
 		if (count($dataset) < 3) throw new Exception('Dataset is too small.');
 
 		// Get items from the first student
 		$items = array();
 		foreach ($this->dataset[0]['items'] as $item) $items[] = $item['name'];
 
 		foreach ($dataset as $student) {
 			// Get items for current student
 			$tmp_items = array();
 			foreach ($student['items'] as $item) $tmp_items[] = $item['name'];
 			// Keep only items in both '$items' AND '$tmp_items'
 			$items = array_intersect($items, $tmp_items);
 		}
 
 		// Now, filter items in the dataset
 		$filtered_dataset = array();
 		foreach ($dataset as $student) {
 			if (!$student['present']) continue;
 			$filtered_items = array();
 			foreach ($student['items'] as $item) {
 				if (in_array($item['name'], $items)) $filtered_items[] = $item;
 			}
 			if (count($filtered_items)) {
 				$student['items'] = $filtered_items;
 				$filtered_dataset[] = $student;
 			}
 		}
 		$dataset = $filtered_dataset;
 		if (count($dataset) < 3) throw new Exception('Dataset is too small.');
 
 		// Compute limits
 		$nb_students = count($dataset);
 		$twenty_seven = (int)($nb_students*27.0/100);
 		$upper_stop = $twenty_seven-1;
 		$lower_start = $nb_students-$twenty_seven+1;
 
 		#echo "$nb_students / $twenty_seven / 0 -> $upper_stop / $lower_start -> $nb_students \n";
 
 		$stats = array();
 		foreach ($dataset as $i => $student) {
 			foreach ($student['items'] as $item) {
 				$name = $item['name'];
 				if (!array_key_exists($name, $stats))
 					$stats[$name] = array(	'27%'	=>		$twenty_seven,
 								'upper' =>		0,
 								'lower' =>		0,
 								'valid' =>		null,
 								'ticked'=>		null,
 								'ticked_count'=>	0,
 								'empty_count'=>		0,
 								'type' =>		null,
 								'subtype' =>		null,
 								'max_points' =>		null,
 								);
 				$stats[$name]['max_points'] = $item['max_points'];
 				$stats[$name]['type'] = $item['type'];
 				$stats[$name]['subtype'] = $item['subtype'];
 
 				// Initialise 'ticked' table
 				if (is_null($stats[$name]['ticked'])) {
 					switch ($stats[$name]['subtype']) {
 						case 'mc':
 							$stats[$name]['ticked'] = array( 'A' => 0, 'B' => 0, 'C' => 0, 'D' => 0, 'multiple' => 0);
 							break;
 						case 'tf':
 							$stats[$name]['ticked'] = array( 'TRUE' => 0, 'FALSE' => 0, 'multiple' => 0);
 							break;
 						default:
 							$stats[$name]['ticked'] = array();
 							break;							
 					}
 				}
 
 				// Count right answers
 				if ($item['right'] > 0) {
 					// Save valid answer
 					if (is_null($stats[$name]['valid'])) {
 						switch ($stats[$name]['subtype']) {
 							case 'tf':
 								if ($item['ticked'] == 'A')
 									$stats[$name]['valid'] = 'TRUE';
 								else
 									$stats[$name]['valid'] = 'FALSE';
 								break;
 							case 'mc':
 								$stats[$name]['valid'] = $item['ticked'];
 								break;
 							case 'open':
 								$stats[$name]['valid'] = 'n/a';
 								break;
 							default:
 								$stats[$name]['valid'] = 'n/a';
 								break;
 						}
 					}
 
 					// 'upper 27%' and 'lower 27%' counters
 					switch ($stats[$name]['subtype']) {
 						case 'mc':
 						case 'tf':
 							if ($i <= $upper_stop) 	$stats[$name]['upper']++;
 							if ($i >= $lower_start) $stats[$name]['lower']++;
 							break;
 						case 'open':
 							if ($i <= $upper_stop)  $stats[$name]['upper'] += $item['points'];
 							if ($i >= $lower_start) $stats[$name]['lower'] += $item['points'];
 							break;
 					}
 				}
 
 				// Count empty answers
 				if (empty($item['ticked'])) {
 					$stats[$name]['empty_count']++;
 				} else {
 					// Stats on non-empty answers
 					$stats[$name]['ticked_count']++;
 					if (strlen($item['ticked']) > 1) {
 						$stats[$name]['ticked'] = $this->createAndIncrement($stats[$name]['ticked'], 'multiple');
 					} else {
 						switch ($item['subtype']) {
 							case 'tf':
 								if ($item['ticked'] == 'A') $field = 'TRUE';
 								if ($item['ticked'] == 'B') $field = 'FALSE';
 								$stats[$name]['ticked'] = $this->createAndIncrement($stats[$name]['ticked'], $field);
 								break;
 							case 'mc':
 								$stats[$name]['ticked'] = $this->createAndIncrement($stats[$name]['ticked'], $item['ticked']);
 								break;
 							default:
 								$stats[$name]['ticked'] = $this->createAndIncrement($stats[$name]['ticked'], $item['ticked']);
 								break;
 						}
 					}
 				}
 			}
 		}
 
 		// Compute more stats
 		$tmp = array();
 		foreach ($stats as $name => $stat) {
 			// Discrimination index
 
 			// For open questions, change the '27%' value.
 			if ($stat['subtype'] == 'open') $stat['27%'] = $stat['27%']*$stat['max_points'];
 
 			$stat['DI'] = ($stat['upper']-$stat['lower'])/(1.0*$stat['27%']);
 
 			// Calculate percentages
 			$ticked_percentage = array();
 			foreach ($stat['ticked'] as $t => $n) {
 				$ticked_percentage[$t] = array( 'n' => $n, '%' => (float)(100.0*$n/$stat['ticked_count']), 'valid' => (int)($t == $stat['valid']));
 			}
 			$stat['ticked'] = $ticked_percentage;
 			$tmp[$name] = $stat;
 		}
 		$stats = $tmp;
 
 		// Print CSV
 		$previous_subtype = null;
 		$header = '"question_id","subtype","27 %","upper","lower","DI","count","valid"';
 		foreach ($stats as $name => $stat) {
 			if ($stat['subtype'] != $previous_subtype) {
 				#if (!is_null($previous_subtype)) echo "\n";
 				echo $header;
 				if ($stat['subtype'] != 'open') {
 					foreach ($stat['ticked'] as $answer => $data) echo ",\"[$answer] count\"";
 					foreach ($stat['ticked'] as $answer => $data) echo ",\"[$answer] %\"";
 				}
 				echo "\n";
 				$previous_subtype = $stat['subtype'];
 			}
 			echo "$name,{$stat['subtype']},{$stat['27%']},{$stat['upper']},{$stat['lower']},{$stat['DI']},{$stat['ticked_count']}";
 			if ($stat['subtype'] == 'open') {
 				echo ",\"n/a\"";
 			} else {
 				foreach ($stat['ticked'] as $answer => $data) if ($data['valid'] == 1) echo ",\"$answer\"";
 				foreach ($stat['ticked'] as $answer => $data) echo ",{$data['n']}";
 				foreach ($stat['ticked'] as $answer => $data) echo ",{$data['%']}";
 			}
 			echo "\n";
 		}
 
 	}
 
 	public function sortByTotalPoints($update = true) {
 		if ($update) {
 			usort($this->dataset, "cmp_total");
 			return $this->dataset;
 		} else {
 			$dataset = $this->dataset;
 			usort($dataset, "cmp_total");
 			return $dataset;
 		}
 	}
 
 	public function getDataSet() {
 		return $this->dataset;
 	}
 
 	protected function createAndIncrement($table, $field, $increment = 1) {
 		if (!array_key_exists($field, $table)) {
 			$table[$field] = 0;
 		}
 		$table[$field] += $increment;
 		return $table;
 	}
 
 	public function getMarks() {
 		$marks = array();
 		foreach($this->dataset as $student) {
 			$tmp = array();
 
 			$tmp['teacher'] = $student['teacher'];
 			$tmp['ID'] = $student['ID'];
 			$tmp['SECTION'] = $student['SECTION'];
 			$tmp['exam_points'] = $student['exam_points'];
 			$tmp['total'] = $student['total'];
 			$tmp['present'] = $student['present'];
 			$tmp['SCIPER'] = $student['SCIPER'];
 			$tmp['quarter_mark6'] = $student['quarter_mark6'];
 			$marks[] = $tmp;
 		}
 		return $marks;
 	}
 
+	public function getQuestions() {
+		$questions = array();
+		foreach($this->dataset as $student) {
+			//print_r($student['items']);
+			$tmp = array();
+
+			$tmp['teacher'] = $student['teacher'];
+			$tmp['ID'] = $student['ID'];
+			$tmp['SECTION'] = $student['SECTION'];
+			$tmp['SCIPER'] = $student['SCIPER'];
+			if (!$student['present']) {
+				$tmp['present'] = "ABS";
+			} else {
+				$tmp['present'] = 1;
+			}
+			$tmp['exam_points'] = $student['exam_points'];
+			$tmp['total'] = $student['total'];
+			# Stats on questions
+			$tmp['nb_questions'] = count($student['items']);
+			$tmp['not_answered'] = 0;
+			$tmp['right'] = 0;
+			$tmp['wrong'] = 0;
+			foreach($student['items'] as $question) {
+				if (empty($question['ticked'])) {
+					// Question was not answered
+					$tmp['not_answered'] += 1;
+				} else {
+					if ($question['right']) $tmp['right'] += 1; else $tmp['wrong'] += 1;
+				}
+			}
+			$questions[] = $tmp;
+		}
+		return $questions;
+	}
+
+
 	public function getStats() {
 		$stats = array();
 
 		# Presence
 		$stats['presence'] = array();
 		$marks = array();
 		$stats['quarter_mark6'] = array( 'n' => 0, 'tot' => 0, 'average' => null, 'stddev' => null, 'median' => null);
 		foreach($this->dataset as $student) {
 
 			// Presence
 			$stats['presence'] = $this->createAndIncrement($stats['presence'], 'total');
 			switch ($student['type']) {
 				case 'student':
 					if ($student['present']) {
 						$stats['presence'] = $this->createAndIncrement($stats['presence'], 'present');
 					} else {
 						$stats['presence'] = $this->createAndIncrement($stats['presence'], 'absent');
 					}
 					break;
 				case 'unused':
 					$stats['presence'] = $this->createAndIncrement($stats['presence'], 'unsused');
 					break;
 				default:
 					$stats['presence'] = $this->createAndIncrement($stats['presence'], 'unknown');
 					
 			}
 
 			// Average
 			if ($student['present']) $marks[] = $student['quarter_mark6'];
 		}
 		$stats['quarter_mark6']['n'] = count($marks);
 		if ($stats['quarter_mark6']['n'] > 0) {
 			$stats['quarter_mark6']['tot'] = array_sum($marks);
 			$stats['quarter_mark6']['average'] = $stats['quarter_mark6']['tot']/$stats['quarter_mark6']['n'];
 			$stats['quarter_mark6']['stddev'] = stats_standard_deviation($marks);
 			if (count($marks) >=3) {
 				sort($marks);
 				$stats['quarter_mark6']['median'] = $marks[round(count($marks)/2)];
 			} else {
 				$stats['quarter_mark6']['median'] = 'n/a';
 			}
 		} else {
 			$stats['quarter_mark6']['tot'] = 0;
 			$stats['quarter_mark6']['average'] = 0;
 			$stats['quarter_mark6']['stddev'] = 0;
 			$stats['quarter_mark6']['median'] = 0;
 		}
 		
 		// Distribution (of marks)
 		$distribution = array();
 		for ($m = 1.0 ; $m <= 6.0 ; $m += 0.25) $distribution[(string)$m] = 0;
 		$stats['distribution_total'] = 0;
 		foreach ($marks as $mark) {
 			$distribution[(string)$mark]++;
 			$stats['distribution_total']++;
 		}
 		$stats['distribution'] = $distribution;
 		$stats['distribution_percentage'] = array();
 		if ($stats['quarter_mark6']['n']) {
 			foreach ($stats['distribution'] as $mark => $count) $stats['distribution_percentage'][$mark] = $count*100.0/$stats['distribution_total'];
 		} else {
 			$stats['distribution_percentage'] = $stats['distribution'];
 		}
 
 		return($stats);
 	}
 
 }
 
 ?>