gistfile1.js

    calculateSeriesAverage: function() {
        var total, firstHour, lastHour, dit, models;

        dit = this;
        total = 0;
        firstTimestamp = this.first().get('timestamp');
        lastTimestamp = this.last().get('timestamp');

        this.each(function(model, i) {
            var width, height, opp, next;

            // Get next setpoint, if there is none, we are at the end of the
            // series and we cannot calculate any more.
            next = dit.at(i + 1);
            if (typeof next === 'undefined') {
                return;
            }

            // Calculate the oppervlakte of this setpoint.
            if (model.get('value') >= next.get('value')) {
                height = next.get('value');
            } else {
                height = model.get('value');
            }

            width = next.get('timestamp') - model.get('timestamp');
            opp = width * height;

            // If the values are not the same, also calculate the remaining
            // triangular part and add it to the total.
            if (model.get('value') !== next.get('value')) {
                height = Math.abs(model.get('value') - next.get('value'));
                opp += width * height * 0.5;
            }
        
            total += opp;
        });

        // Divide by number of hours between first and last setpoint.
        return Math.round(total * 10 / (lastTimestamp - firstTimestamp)) / 10;
    }