Portsmouth University Classification Calculator

classifier.js

/*
  run with:
  portsmouthClassifier.classify(marks);
*/

var portsmouthClassifier = (function() {

  var totalCredits = function(year) {
		return _.reduce(year, function(memo, unit) {
			return memo + unit.credits;
		}, 0);
	};

	var sortByGrade = function(year) {
		return _.sortBy(year, function(unit) { return -unit.grade; });
	};

	var cloneYearMarks = function(year) {
		var clone = year.slice(0);
		return _.map(clone, function(unit) { return _.clone(unit); });
	};

	var sumGrades = function(year) {
		return _.reduce(year, function(memo, unit) {
			return memo + unit.grade;
		}, 0);
	};

	var grader = function(mark) {
		var grade;

		if (mark <= 39) {
			grade = 'Fail';
		}
		else if (mark >= 40 && mark <= 49) {
			grade = '3rd';
		}
		else if (mark >= 50 && mark <= 59) {
			grade = '2:2';
		}
		else if (mark >= 60 && mark <= 69) {
			grade = '2:1';
		}
		else if (mark >= 70) {
			grade = '1st';
		}

		return grade;
	};

	var removeWorst20Credits = {
		// these two can be combined, but i'm too tired
		year2: function(yearIn) {
			var year = cloneYearMarks(yearIn);
			year = _.initial(sortByGrade(year));

			// worst unit was 20 credits, we're done here
			if (totalCredits(year) == 100) {
				return year;
			}

			// worst 2 units were each 10 credits, take em off
			var lastUnit = _.last(year);
			if (lastUnit.credits == 10) {
				return _.initial(year);
			}

			// worst unit was 10 credit
			// second worst was 20 credit - now worth just 10
			year = _.initial(year);
			lastUnit.credits = 10;

			year.push(lastUnit);

			var checkCredits = totalCredits(year);
			if (checkCredits != 100) {
				throw new Error('totalCredits is '+checkCredits+' not 100');
			}

			return year;
		},
		year3: function(yearIn) {
			var year = cloneYearMarks(yearIn);
			year = sortByGrade(year);
			var lastUnit = _.last(year);
			year = _.initial(year);

			// worst unit was 20 credits
			if (totalCredits(year) == 100) {
				return year;
			}

			// worst unit was 40 credits
			// it's now just worth 20
			lastUnit.credits = 20;
			year.push(lastUnit);

			var checkCredits = totalCredits(year);
			if (checkCredits != 100) {
				throw new Error('totalCredits is '+checkCredits+' not 100');
			}

			return year;
		}
	};

	var classifiers = {
		ruleA: function(grades) {
			var y2 = removeWorst20Credits.year2(grades.year2);
			var y3 = removeWorst20Credits.year3(grades.year3);

			var meanY2 = sumGrades(y2) / y2.length;
			var meanY3 = sumGrades(y3) / y3.length;

			return Math.round((meanY2 / 100 * 40) + (meanY3 / 100 * 60));
		},

		ruleB: function(grades) {
			var y3 = removeWorst20Credits.year3(grades.year3);
			return Math.round(sumGrades(y3) / y3.length);
		},

		ruleC: function(grades) {
			var y2 = removeWorst20Credits.year2(grades.year2);
			var y3 = removeWorst20Credits.year3(grades.year3);

			// combine them & sort them
			var join = sortByGrade(y2.concat(y3));

			// grab 50 credits worth of units
			var creditCount = 0,
				i = 0,
				top50 = [],
				tempUnit;

			while (creditCount < 100) {
				tempUnit = join[i];
				creditCount += tempUnit.credits;
				top50.push(tempUnit);
				i++;
			}

			// take bottom grade
			return Math.round(_.last(top50).grade);
		}
	};

	return {
		classify: function(marks) {
			var results = [
				classifiers.ruleA(marks),
				classifiers.ruleB(marks),
				classifiers.ruleC(marks)
			];

			var result = _.first(_.sortBy(results, function(r) { return -r; }));

			var grade = grader(result);

			return {
				grade: grade,
				result: result+'%',
				details: {
					ruleA: results[0],
					ruleB: results[1],
					ruleC: results[2]
				}
			};
		}
	};

})();

grades.js

/*
  this file demonstrates the input format the classifier expects
  (grade is the percentage achieved for the unit)
*/

var marks = {
  "year2": [
		{
			"title": "Web Client and Server Programming",
			"credits": 20,
			"grade": 90
		},
		{
			"title": "Application Usability for Desktop and Web",
			"credits": 20,
			"grade": 40
		},
		{
			"title": "Web Foundations",
			"credits": 10,
			"grade": 70
		},
		{
			"title": "Web Server Use, Configuration and Management",
			"credits": 10,
			"grade": 100
		},
		{
			"title": "Databases 20",
			"credits": 20,
			"grade": 42
		},
		{
			"title": "Advanced Programming and Data Structures",
			"credits": 20,
			"grade": 30
		},
		{
			"title": "Web Engineering and Project Management",
			"credits": 20,
			"grade": 40
		}
	],
	"year3": [
		{
			"title": "Web Research",
			"credits": 20,
			"grade": 40
		},
		{
			"title": "Enterprise Web Applications",
			"credits": 20,
			"grade": 40
		},
		{
			"title": "Data Warehousing and Mining",
			"credits": 20,
			"grade": 40
		},
		{
			"title": "Distributed Systems and Parallel Programming",
			"credits": 20,
			"grade": 40
		},
		{
			"title": "Final Year Project",
			"credits": 40,
			"grade": 40
		}
	]
};