MDL-14201 "Summary graph" included a summary graph at the bottom of overview report page. Shows the distribution of grades achieved by students. If a group is selected the grades from the group are compared with the grades for all participants.

lang/en_utf8/quiz_overview.php

@@ -15,6 +15,7 @@ $string['optonlygradedattempts'] = 'only the attempt that is graded for each use
 $string['overview'] = 'Overview';
 $string['overviewdownload'] = 'Overview download';
 $string['overviewdownload'] = 'Overview download';
+$string['overviewreportgraph'] = 'Bar Graph of Number of Students Achieving Grade Ranges';
 $string['pagesize'] = 'Page size';
 $string['preferencespage'] = 'Preferences just for this page';
 $string['preferencessave'] = 'Save preferences';

mod/quiz/report/overview/overviewgraph.php

@@ -0,0 +1,92 @@
+<?php  // $Id$
+include '../../../../config.php';
+include $CFG->dirroot."/lib/graphlib.php";
+include $CFG->dirroot."/mod/quiz/report/reportlib.php";
+
+$quizid = required_param('id', PARAM_INT);
+
+$quiz = get_record('quiz', 'id', $quizid);
+$course = get_record('course', 'id', $quiz->course);
+require_login($course);
+$cm = get_coursemodule_from_instance('quiz', $quizid);
+$currentgroup = groups_get_activity_group($cm);
+
+$modcontext = get_context_instance(CONTEXT_MODULE, $cm->id);
+require_capability('mod/quiz:viewreports', $modcontext);
+
+$line = new graph(640,480);
+$line->parameter['title']   = '';
+$line->parameter['y_label_left'] = $course->students;
+$line->parameter['x_label'] = get_string('grade');
+$line->parameter['y_label_angle'] = 90;
+$line->parameter['x_label_angle'] = 0;
+$line->parameter['x_axis_angle'] = 60;
+
+//following two lines seem to silence notice warnings from graphlib.php
+$line->y_tick_labels = null;
+$line->offset_relation = null;
+
+$line->parameter['bar_size']    = 1.5; // make size > 1 to get overlap effect
+$line->parameter['bar_spacing'] = 20; // don't forget to increase spacing so that graph doesn't become one big block of colour
+
+//pick a sensible number of bands depending on quiz maximum grade.
+$bands = $quiz->grade;
+while ($bands >= 20 || $bands < 10){
+    if ($bands >= 50){
+        $bands = $bands /5;
+    } else if ($bands >= 20) {
+        $bands = $bands /2;
+    }
+    if ($bands < 4){
+        $bands = $bands * 5;
+    } else if ($bands < 10){
+        $bands = $bands * 2;
+    }
+}
+
+$bandwidth = $quiz->grade / $bands;
+$bandlabels = array();
+for ($i=0;$i < $quiz->grade;$i += $bandwidth){
+    $bandlabels[] = number_format($i, $quiz->decimalpoints).' - '.number_format($i+$bandwidth, $quiz->decimalpoints);
+} 
+$line->x_data          = $bandlabels;
+
+$useridlist = join(',',array_keys(get_users_by_capability($modcontext, 'mod/quiz:attempt','','','','','','',false)));
+$line->y_data['allusers'] = quiz_report_grade_bands($bands, $quizid, $useridlist);
+if ($currentgroup){
+    //only turn on legends if there is more than one set of bars
+    $line->parameter['legend']        = 'outside-top';
+    $line->parameter['legend_border'] = 'black';
+    $line->parameter['legend_offset'] = 4;
+    $useridingrouplist = join(',',array_keys(get_users_by_capability($modcontext, 'mod/quiz:attempt','','','','',$currentgroup,'',false)));
+    $line->y_data['groupusers'] = quiz_report_grade_bands($bands, $quizid, $useridingrouplist);
+    $line->y_format['groupusers'] =
+        array('colour' => 'green', 'bar' => 'fill', 'shadow_offset' => 1, 'legend' => groups_get_group_name($currentgroup));
+    $line->y_order = array('allusers', 'groupusers');
+} else {
+    $line->y_order = array('allusers');
+}
+
+
+$line->y_format['allusers'] =
+  array('colour' => 'red', 'bar' => 'fill', 'shadow_offset' => 1, 'legend' => get_string('allparticipants'));
+
+
+$line->parameter['y_min_left'] = 0;  // start at 0
+$line->parameter['y_max_left'] = max($line->y_data['allusers']); 
+$line->parameter['y_decimal_left'] = 0; // 2 decimal places for y axis.
+
+
+//pick a sensible number of gridlines depending on max value on graph.
+$gridlines = max($line->y_data['allusers']);
+while ($gridlines >= 10){
+    if ($gridlines >= 50){
+        $gridlines = $gridlines /5;
+    } else {
+        $gridlines = $gridlines /2;
+    }
+}
+
+$line->parameter['y_axis_gridlines'] = $gridlines+1; 
+$line->draw();
+?>

mod/quiz/report/overview/report.php

@@ -622,6 +622,9 @@ document.getElementById("noscriptmenuaction").style.display = "none";
             // Print display options
             $mform->set_data($displayoptions +compact('detailedmarks', 'pagesize'));
             $mform->display();
+            $imageurl = $CFG->wwwroot.'/mod/quiz/report/overview/overviewgraph.php?id='.$quiz->id;
+            print_heading(get_string('overviewreportgraph', 'quiz_overview'));
+            echo '<div class="mdl-align"><img src="'.$imageurl.'" alt="'.get_string('overviewreportgraph', 'quiz_overview').'" /></div';
         }
         return true;
     }

mod/quiz/report/reportlib.php

@@ -102,4 +102,22 @@ function quiz_report_qm_filter_subselect($quizgrademethod){
     }
     return $qmsubselect;
 }
+
+function quiz_report_grade_bands($bands, $quizid, $useridlist){
+    $sql = "SELECT
+        FLOOR(qg.grade*$bands/q.grade) AS band,
+        COUNT(1) AS num
+    FROM
+        mdl_quiz_grades qg, 
+        mdl_quiz q
+    WHERE qg.quiz = q.id AND quiz = $quizid AND qg.userid IN ($useridlist)
+    GROUP BY band
+    ORDER BY band";
+    $data = get_records_sql_menu($sql);
+    //need to create array elements with values 0 at indexes where there is no element
+    $data =  $data + array_fill(0, $bands, 0);
+    ksort($data);
+    return $data;
+}
+
 ?>