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workshop: fixed two grading evaluation errors
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The first one was caused by the wrong rounding. The second one caused
the best assessment not being recognized properly.
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@mudrd8mz
mudrd8mz committed Jan 4, 2010
1 parent d864fdf commit f0ec02a
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Showing 2 changed files with 72 additions and 11 deletions.
10 changes: 6 additions & 4 deletions mod/workshop/eval/best/lib.php
View file
Original file line number Diff line number Diff line change
Expand Up @@ -173,7 +173,7 @@ protected function process_assessments(array $assessments, array $diminfo, stdCl
$best = $assessments[$bestid];
foreach ($assessments as $asid => $assessment) {
$d = $this->assessments_distance($assessment, $best, $diminfo, $settings);
if (!isset($distances[$asid]) or $d < $distances[$asid]) {
if (!is_null($d) and (!isset($distances[$asid]) or $d < $distances[$asid])) {
$distances[$asid] = $d;
}
}
Expand Down Expand Up @@ -353,12 +353,14 @@ protected function weighted_variance(array $assessments) {
* The passed data structures must contain ->dimgrades property. The referential
* assessment is supposed to be close to the average assessment. All dimension grades are supposed to be
* normalized to the interval 0 - 100.
* Returned value is rounded to 4 valid decimals to prevent some rounding issues - see the unit test
* for an example.
*
* @param stdClass $assessment the assessment being measured
* @param stdClass $referential assessment
* @param array $diminfo of stdClass(->weight ->min ->max ->variance) indexed by dimension id
* @param stdClass $settings
* @return float|null rounded to 5 valid decimals
* @return float|null rounded to 4 valid decimals
*/
protected function assessments_distance(stdClass $assessment, stdClass $referential, array $diminfo, stdClass $settings) {
$distance = 0;
Expand All @@ -368,18 +370,18 @@ protected function assessments_distance(stdClass $assessment, stdClass $referent
$rgrade = $referential->dimgrades[$dimid];
$var = $diminfo[$dimid]->variance;
$weight = $diminfo[$dimid]->weight;
$n += $weight;

// variations very close to zero are too sensitive to a small change of data values
if ($var > 0.01 and $agrade != $rgrade) {
$absdelta = abs($agrade - $rgrade);
$reldelta = pow($agrade - $rgrade, 2) / ($settings->comparison * $var);
$distance += $absdelta * $reldelta * $weight;
$n += $weight;
}
}
if ($n > 0) {
// average distance across all dimensions
return grade_floatval($distance / $n);
return round($distance / $n, 4);
} else {
return null;
}
Expand Down
73 changes: 66 additions & 7 deletions mod/workshop/eval/best/simpletest/testlib.php
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,9 @@ public function average_assessment(array $assessments) {
public function weighted_variance(array $assessments) {
return parent::weighted_variance($assessments);
}

public function assessments_distance(stdClass $assessment, stdClass $referential, array $diminfo, stdClass $settings) {
return parent::assessments_distance($assessment, $referential, $diminfo, $settings);
}
}

class workshop_best_evaluation_test extends UnitTestCase {
Expand Down Expand Up @@ -131,23 +133,39 @@ public function test_normalize_grades_max_equals_min() {
$this->assertEqual($norm[1]->dimgrades[3], 100);
}

public function test_average_assessment() {
public function test_average_assessment_same_weights() {
// fixture set-up
$assessments = array();
$assessments[18] = (object)array(
'weight' => 1,
'dimgrades' => array(1 => 50, 2 => 33.33333),
);
$assessments[16] = (object)array(
'weight' => 1,
'dimgrades' => array(1 => 0, 2 => 66.66667),
);
// excersise SUT
$average = $this->evaluator->average_assessment($assessments);
// validate
$this->assertIsA($average->dimgrades, 'array');
$this->assertEqual(grade_floatval($average->dimgrades[1]), grade_floatval(25));
$this->assertEqual(grade_floatval($average->dimgrades[2]), grade_floatval(50));
}

public function test_average_assessment_different_weights() {
// fixture set-up
$assessments = array();
$assessments[11] = (object)array(
'weight' => 1,
'dimgrades' => array(3 => 10.0, 4 => 13.4, 5 => 95.0),
'dimweights' => array(3 => 1, 4 => 1, 5 => 1)
);
$assessments[13] = (object)array(
'weight' => 3,
'dimgrades' => array(3 => 11.0, 4 => 10.1, 5 => 92.0),
'dimweights' => array(3 => 1, 4 => 1, 5 => 1)
);
$assessments[17] = (object)array(
'weight' => 1,
'dimgrades' => array(3 => 11.0, 4 => 8.1, 5 => 88.0),
'dimweights' => array(3 => 1, 4 => 1, 5 => 1)
);
// excersise SUT
$average = $this->evaluator->average_assessment($assessments);
Expand All @@ -164,12 +182,10 @@ public function test_average_assessment_noweight() {
$assessments[11] = (object)array(
'weight' => 0,
'dimgrades' => array(3 => 10.0, 4 => 13.4, 5 => 95.0),
'dimweights' => array(3 => 1, 4 => 1, 5 => 1)
);
$assessments[17] = (object)array(
'weight' => 0,
'dimgrades' => array(3 => 11.0, 4 => 8.1, 5 => 88.0),
'dimweights' => array(3 => 1, 4 => 1, 5 => 1)
);
// excersise SUT
$average = $this->evaluator->average_assessment($assessments);
Expand Down Expand Up @@ -207,4 +223,47 @@ public function test_weighted_variance() {
// dimension [4] represents data 2, 4, 4, 4, 5, 5, 7, 9 having stdev=2 (stdev is sqrt of variance)
$this->assertEqual($variance[4], 4);
}

public function test_assessments_distance_zero() {
// fixture set-up
$diminfo = array(
3 => (object)array('weight' => 1, 'min' => 0, 'max' => 100, 'variance' => 12.34567),
4 => (object)array('weight' => 1, 'min' => 1, 'max' => 5, 'variance' => 98.76543),
);
$assessment1 = (object)array('dimgrades' => array(3 => 15, 4 => 2));
$assessment2 = (object)array('dimgrades' => array(3 => 15, 4 => 2));
$settings = (object)array('comparison' => 5);
// excersise SUT and validate
$this->assertEqual($this->evaluator->assessments_distance($assessment1, $assessment2, $diminfo, $settings), 0);
}

public function test_assessments_distance_equals() {
/*
// fixture set-up
$diminfo = array(
3 => (object)array('weight' => 1, 'min' => 0, 'max' => 100, 'variance' => 12.34567),
4 => (object)array('weight' => 1, 'min' => 0, 'max' => 100, 'variance' => 12.34567),
);
$assessment1 = (object)array('dimgrades' => array(3 => 25, 4 => 4));
$assessment2 = (object)array('dimgrades' => array(3 => 75, 4 => 2));
$referential = (object)array('dimgrades' => array(3 => 50, 4 => 3));
$settings = (object)array('comparison' => 5);
// excersise SUT and validate
$this->assertEqual($this->evaluator->assessments_distance($assessment1, $referential, $diminfo, $settings),
$this->evaluator->assessments_distance($assessment2, $referential, $diminfo, $settings));
*/
// fixture set-up
$diminfo = array(
1 => (object)array('min' => 0, 'max' => 2, 'weight' => 1, 'variance' => 625),
2 => (object)array('min' => 0, 'max' => 3, 'weight' => 1, 'variance' => 277.7778888889),
);
$assessment1 = (object)array('dimgrades' => array(1 => 0, 2 => 66.66667));
$assessment2 = (object)array('dimgrades' => array(1 => 50, 2 => 33.33333));
$referential = (object)array('dimgrades' => array(1 => 25, 2 => 50));
$settings = (object)array('comparison' => 9);
// excersise SUT and validate
$this->assertEqual($this->evaluator->assessments_distance($assessment1, $referential, $diminfo, $settings),
$this->evaluator->assessments_distance($assessment2, $referential, $diminfo, $settings));

}
}

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