MetricsChartView.js

/*global define */
define(['jquery', 'underscore', 'backbone', 'd3'],
    function($, _, Backbone, d3) {
    'use strict';

    /*
    * The MetricsChartView will render an SVG times-series chart using D3 that shows the number of metrics over time.
    */
    var MetricsChartView = Backbone.View.extend({

        initialize: function (options) {

            if(!d3){ console.log('SVG is not supported'); return null; }

            if(typeof options !== "undefined"){

            this.model        = options.model         || null;    // TODO: figure out how to set the model on this view

            this.metricCount  = options.metricCount   || "0";     // for now, use individual arrays
            this.metricMonths = options.metricMonths  || "0";
            this.id           = options.id            || "metrics-chart";
            this.width        = options.width         || 600;
            this.height       = options.height        || 370;
            this.metricName   = options.metricName;

        }
      },

      // http://stackoverflow.com/questions/9651167/svg-not-rendering-properly-as-a-backbone-view
      // Give our el a svg namespace because Backbone gives a different one automatically
      nameSpace: "http://www.w3.org/2000/svg",
        _ensureElement: function() {
           if (!this.el) {
              var attrs = _.extend({}, _.result(this, 'attributes'));
              if (this.id) attrs.id = _.result(this, 'id');
              if (this.className) attrs['class'] = _.result(this, 'className');
              var $el = $(window.document.createElementNS(_.result(this, 'nameSpace'), _.result(this, 'tagName'))).attr(attrs);
              this.setElement($el, false);
           } else {
              this.setElement(_.result(this, 'el'), false);
           }
       },

      tagName: "svg",

    render: function(){

        /*
        * ========================================================================
        *  NAMING CONVENTIONS:

        CONTEXT: Context refers to the mini slider chart at the bottom, that includes the d3 "brush"
        FOCUS: Focus refers to the larger main chart at the top
        BRUSH: The rectangle in the context chart that highlights what is currently in focus in the focus chart.

        * ========================================================================
        */

        // check if there have been any views/citations
        var sumMetricCount = 0;
        for (var i = 0; i < this.metricCount.length; i++) {
            sumMetricCount += this.metricCount[i]
        }

        // when ther no data or no views/citations yet, just show some text:
        if(this.metricCount.length == 0 || this.metricCount == 0 || sumMetricCount ==0){

            var metricNameLemma = this.metricName.toLowerCase().substring(0, this.metricName.length - 1);
            var textMessage = "This dataset hasn’t been " + metricNameLemma + "ed yet."

            var margin	= {top: 25, right: 40, bottom: 40, left: 40},
                width	= this.width - margin.left - margin.right,
                height	= this.height - margin.top - margin.bottom;

            var vis = d3.select(this.el)
                .attr("width", width + margin.left + margin.right)
                .attr("height", height + margin.top + margin.bottom)
              	.attr("class", "line-chart no-data");

            var bkg = vis.append("svg:rect")
                .attr("class", "no-data")
                .attr("width", width)
                .attr("height", height)
                .attr("rx", 2)
                .attr("ry", 2)
                .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

            var msg = vis.append("text")
                .attr("class", "no-data")
                .text(textMessage)
                .attr("text-anchor", "middle")
                .attr("font-size", "20px")
                .attr("x", width/2)
                .attr("y", height/2)
                .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

        // if there is data (even a series of zeros), draw the time-series chart:
    } else {

        /*
        * ========================================================================
        *  Global variables and options
        * ========================================================================
        */

        var metricName = this.metricName;

        // the format of the date in the input data
        var input_date_format 	  =		d3.time.format("%Y-%m");
        // how dates will be displayed in the chart in most cases
        var display_date_format	  = 	d3.time.format("%b %Y");

        // the length of a day/year in milliseconds
        var day_in_ms = 86400000,
        	year_in_ms = 31540000000;

        // focus chart sizing
        var margin	= {top: 30, right: 30, bottom: 95, left: 20},
            width	= this.width - margin.left - margin.right,
            height	= this.height - margin.top - margin.bottom;

        // context chart sizing
        var margin_context = {top: 315, right: 30, bottom: 20, left: 20},
            height_context = this.height - margin_context.top - margin_context.bottom;

        // zoom button sizing
        var button_width = 40,
        	button_height = 14,
        	button_padding = 10;

        // how wide does the tooltip div need to be to accomdate text?
        var tooltip_width = 76;

        // what proportion of a month should a bar cover?
        var bar_width_factor = 0.8;

        /*
        * ========================================================================
        *  Prepare data
        * ========================================================================
        */

        // change dates to milliseconds, to enable calculating the `d3.extent`
        var metricMonths_parsed = [];
        this.metricMonths.forEach(function(part, index, theArray) {
          metricMonths_parsed[index] = input_date_format.parse(part).getTime();
        });

        // input data from model doesn't list months where there were 0 counts for all metrics (views/downloads/citations)
        // construct an array of all months between min and max dates to use as x variable
        var all_months = d3.time.scale()
        				.domain(d3.extent(metricMonths_parsed))
                        .ticks(d3.time.months, 1);

        // add padding to both sides of array so that bars don't get cut off.
        // add more padding when there's just one bar (otherwise it's too wide)
        if (metricMonths_parsed.length == 1) {
            var new_min_date = new Date(d3.extent(metricMonths_parsed)[0] - day_in_ms*13),
                new_max_date = new Date(d3.extent(metricMonths_parsed)[1] + day_in_ms*31*bar_width_factor + day_in_ms*13);
        } else {
            var new_min_date = new Date(d3.extent(metricMonths_parsed)[0] - day_in_ms*1),
                new_max_date = new Date(d3.extent(metricMonths_parsed)[1] + day_in_ms*31*bar_width_factor);
        };

        all_months.push(new_min_date);
        // also add a little padding on the left for consistency
        all_months.push(new_max_date);

        // for each month, check whether there is a count available,
        // if so append it, otherwise append zero.
        var dataset = [];
        for(var i=0; i<all_months.length; i++){
        	var match_index = metricMonths_parsed.indexOf(all_months[i].getTime());
        	if (match_index == -1) { // no match in data
        		dataset.push({integer: i, month: all_months[i], count:0});
        	} else { // match in data
        		dataset.push({integer: i, month: all_months[i], count:this.metricCount[match_index]});
        	}
        };

        /*
        * ========================================================================
        *  x and y coordinates
        * ========================================================================
        */

        var x_full_extent = d3.extent(dataset, function(d) { return d.month; });
        var bar_width = ((day_in_ms*30)/(x_full_extent[1]-x_full_extent[0])) * width * bar_width_factor;

        /* === Focus Chart === */

        var x = d3.time.scale()
            .range([0,width])
            .domain(d3.extent(dataset, function(d) { return d.month; }));

        var y = d3.scale.linear()
        	.range([height, 0])
            .domain([0, d3.max(dataset, function(d) { return d.count; })*1.04]);

        var x_axis = d3.svg.axis()
        	.scale(x)
            .orient("bottom")
        	.tickSize(-(height))
            .ticks(generate_ticks)
        	.tickFormat(format_months);

        var y_axis = d3.svg.axis()
        	.scale(y)
            .ticks(4)
        	.tickFormat(d3.format("d"))
            .tickSize(-(width))
        	.orient("right");

        /* === Context Chart === */

        var x_context = d3.time.scale()
            .range([0, width])
            .domain(d3.extent(dataset, function(d) { return d.month; }));

        var y_context = d3.scale.linear()
        	.range([height_context, 0])
            .domain(y.domain());

        var x_axis_context = d3.svg.axis()
            .scale(x_context)
            .orient("bottom")
            .ticks(generate_ticks)
            .tickFormat(format_months);

        /*
        * ========================================================================
        *  Variables for brushing and zooming behaviour
        * ========================================================================
        */

        var brush = d3.svg.brush()
            .x(x_context)
            .on("brush", change_focus_brush)
            .on("brushend", check_bounds);

        var zoom = d3.behavior.zoom()
            .on("zoom", change_focus_zoom)
            .on("zoomend", check_bounds);

        /*
        * ========================================================================
        *  Define the SVG area ("vis") and append all the layers
        * ========================================================================
        */

        // === the main components === //

        var vis = d3.select(this.el)
            .attr("width", width + margin.left + margin.right)
            .attr("height", height + margin.top + margin.bottom)
          	.attr("class", "line-chart");

        // clipPath is used to keep elements from moving outside of plot area when viwer zooms/scrolls/brushes
        vis.append("defs").append("clipPath")
            .attr("id", "clip")
            .append("rect")
            .attr("width", width)
            .attr("height", height);

        var pane = vis.append("rect")
            .attr("class", "pane")
            .attr("width", width)
            .attr("height", height)
            .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

        var context = vis.append("g")
            .attr("class", "context")
            .attr("transform", "translate(" + margin_context.left + "," + margin_context.top + ")");

        var focus = vis.append("g")
            .attr("class", "focus")
            .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

        // === current date range text & zoom buttons === //

        var expl_text = vis.append("g")
            .attr("id", "buttons_group")
            .attr("transform", "translate(" + 0 + ","+ 0 +")");

        expl_text.append("text")
        	.attr("id", "totalCount")
            .style("text-anchor", "start")
            .attr("transform", "translate(" + 18 + ","+ 11 +")");

        expl_text.append("text")
            .attr("id", "displayDates")
            .style("text-anchor", "start")
            .attr("transform", "translate(" + 20 + ","+ 22 +")");

        update_context();

        // === the zooming/scaling buttons === //

        if ((x_full_extent[1] - x_full_extent[0]) < year_in_ms) {
            var button_data =["month","all"];
        } else {
           var button_data =["year","month","all"];
        };

        var button_count	 = button_data.length -1,
        	button_g_width	 =	(button_count*button_width) +
        						(button_count*button_padding) +
        						margin.right - button_padding;

        expl_text.append("text")
        	.attr("class", "zoomto_text")
            .text("Zoom to")
            .style("text-anchor", "start")
            .attr("transform", "translate(" + (width - button_g_width - 45) + ","+ 14 +")")
        	.style("opacity", "0");

        var button = expl_text.selectAll("g")
            .data(button_data)
            .enter().append("g")
            .attr("class", "scale_button")
            .attr("transform", function(d, i) { return "translate(" + ((width - button_g_width) + i*button_width + i*button_padding) + ",4)"; })
        	.style("opacity", "0");

        button.append("rect")
        	.attr("class", "button_rect")
        	.attr("width", button_width)
        	.attr("height", button_height)
            .attr("rx", 1)
            .attr("ry", 1);

        button.append("text")
            .attr("dy", (button_height/2 + 3))
            .attr("dx", button_width/2)
            .style("text-anchor", "middle")
            .text(function(d) { return d; });

        /* === focus chart === */

        focus.append("g")
            .attr("class", "y axis")
            .call(y_axis)
           	.attr("transform", "translate(" + (width) + ", 0)")
        	.style("text-anchor", "middle");

        // x-axis
        focus.append("g")
            .attr("class", "x axis")
            .attr("transform", "translate(0," + height + ")")
            .call(x_axis)
        	.style("text-anchor", "middle");

        // enter bars
        focus.selectAll(".bar")
        	.data(dataset)
        	.enter().append("rect")
        	  		.attr("class", "bar")
        			  .attr("id", function(d){return "bar_" + d.month.getTime()}) //id of each bar is "bar_" plus it's associated date in ms
        	  		.attr("x", function (d) {return x(d.month); })
        	  		.attr("y", height)
        	  		.attr("height", 0)
        	  		.attr("width", bar_width)
        			.style("opacity", 0)
        			.on("mouseover", function(d) {
        				var floor_month = d3.time.month.floor(d.month).getTime();
        				highlight_bar("#bar_" + floor_month);
        				highlight_label("#label_" + floor_month);
        				show_tooltip(d);
        			})
        			.on("mouseout", function(d) {
        				var floor_month = d3.time.month.floor(d.month).getTime();
        				unhighlight_bar("#bar_" + floor_month);
        				unhighlight_label("#label_" + floor_month);
        				hide_tooltip(d);
        			});

        // animate bars
        focus.selectAll(".bar")
        	.transition()
        	.duration(450)
        	.ease("elastic", 1.03, 0.98)
        	.delay(function(d, i) {
        		var max_delay = 600;
        		var z = i / (dataset.length-1);
        		var line_z =  z * max_delay * 0.4;
        		var log_z = Math.log2(z + 1) * max_delay * 0.6;
        		return(250+line_z + log_z);
        	})
        	.attr("y", function (d) {return y(d.count);	  		})
        	.attr("height", function (d) {return y(0) - y(d.count);	  		})
        	.style("opacity", 1);

        /* === context chart === */

        // enter context bars
        context.selectAll(".bar_context")
        	.data(dataset)
        	.enter().append("rect")
        	  		.attr("class", "bar_context")
        	  		.attr("x", function (d) {return x_context(d.month) })
        	  		.attr("y", height_context)
        	  		.attr("height", 0)
        	  		.attr("width", bar_width)
        			.style("opacity", 0);

        // animate context bars
        context.selectAll(".bar_context")
        	.transition()
        	.duration(450)
        	.ease("elastic", 1.03, 0.98)
        	.delay(function(d, i) {
        		var max_delay = 600;
        		var z = i / (dataset.length-1);
        		var line_z =  z * max_delay * 0.4;
        		var log_z = Math.log2(z + 1) * max_delay * 0.6;
        		return(line_z + log_z);
        	})
        	.attr("y", function (d) {return y_context(d.count);	  		})
        	.attr("height", function (d) {return y_context(0) - y_context(d.count);	  		})
        	.style("opacity", 1);

        // x-axis
        context.append("g")
            .attr("class", "x axis")
            .attr("transform", "translate(0," + height_context + ")")
            .call(x_axis_context);

        /* === brush  === */

        var brushg = context.append("g")
            .attr("class", "x brush")
            .call(brush);

        brushg.selectAll(".extent")
        	.attr("y", -6)
        	.attr("height", height_context + 8)
        	.style("opacity" , "0");

        brushg.selectAll(".resize")
            .append("rect")
            .attr("class", "handle")
            .attr("transform", "translate(0," +  -3 + ")")
            .attr('rx', 1)
        	.attr('ry', 1)
            .attr("height", 0)
            .attr("width", 3)
        	.style("opacity" , "0");

        brushg.selectAll(".resize")
            .append("rect")
            .attr("class", "handle-mini")
            .attr("transform", "translate(-2,8.5)")
            .attr('rx', 2)
            .attr('ry', 2)
            .attr("height", 0)
            .attr("width", 7)
        	.style("opacity" , "0");

        /* === y axis title === */
        vis.append("text")
            .attr("class", "y axis title")
            .text("Monthly " + this.metricName)
            .attr("x", (-((height+margin.top+margin.bottom-50)/2)))
            .attr("y", 0)
            .attr("dy", "1em")
            .attr("transform", "rotate(-90)")
            .style("text-anchor", "middle");

        // allow zoom, brush, and scale behavior after a small delay,
        // so that user does not interrupt bar entrance animation.
        // show UI elements only once user is able to interact with them.
        setTimeout(function(){

        	// add behaviours
        	pane.call(zoom)
        		.call(change_focus_zoom);
        	zoom.x(x);

        	vis.selectAll(".scale_button")
        		.style("cursor", "pointer")
        		.on("click", zoom_to_interval);

        	// fade in buttons
        	vis.selectAll(".scale_button,.zoomto_text")
        		.transition()
        		.duration(100)
        		.ease("cubic")
        		.style("opacity","1");

        	// fade in brush elements
        	brushg.selectAll(".extent")
        		.transition()
        		.duration(100)
        		.ease("cubic")
        		.style("opacity" , "1");

        	brushg.selectAll(".handle-mini")
        		.transition()
        		.duration(170)
        		.ease("linear")
        		.attr("height", (height_context/2))
        		.style("opacity" , "1");

        	brushg.selectAll(".handle")
        		.transition()
        		.duration(170)
        		.ease("linear")
        		.attr("height", height_context + 6)
        		.style("opacity" , "1");

            // tooltip div must be created after timeout so that parent div
            // has time to load (otherwise can't select .metric-chart div)
            d3.select(".metric-chart")
                .append("div")
                    .attr("class", "metric_tooltip")
                    .style("opacity", 0)
                    .style("width", tooltip_width + "px");
        	},
        900);

        /*
        * ========================================================================
        *  Functions
        * ========================================================================
        */

        /*	------------------------------------------------------
        		HELPER FUNCTIONS
        	------------------------------------------------------  */

        function get_zoom_scale(){
        // custom zoom scale needed to calculate width of bars with zoom/brush.
        // can't use zoom.scale() because this needs to be reset (to one) when using change_focus_brush()
        	var x_current_width = x.domain()[1] - x.domain()[0],
        		x_total_width = x_full_extent[1] - x_full_extent[0],
        		zoom_scale = x_total_width/x_current_width;
        	return(zoom_scale);
        };

        function convert_metric_name(n){
        // remove s from metric name if count is 1
        	if (n == 1) {
        		return metricName.slice(0, -1);
        	} else {
        		return metricName;
        	}
        };

        /*	------------------------------------------------------
        		HOVER BEHAVIOUR: X-AXIS LABELS, BARS, TOOLTIPS
        	------------------------------------------------------  */

        function highlight_bar(bar_id){
        // mouseover effect on bar
        	focus.select(bar_id)
        		.style("stroke-width", "1")
        		.style("opacity", "0.9");
        };

        function unhighlight_bar(bar_id) {
        // undo mouseover effect on bar
        	focus.select(bar_id)
        		.style("stroke-width", "0")
        		.style("opacity", "1");
        };

        function highlight_label(label_id){
        // mouseover effect on label
        	focus.select(label_id).selectAll("text")
        		.style("font-weight", "bold");
        };

        function unhighlight_label(label_id){
        // undo mouseover effect on label
        	focus.select(label_id).selectAll("text")
        		.style("font-weight", "normal");
        };

        function add_tick_behaviour() {
        // adds html ID and hover behaviour to the x-axis ticks/labels
        // this function is called each time these labels/ticks are re-generated.

        	focus.selectAll(".x.axis .tick")[0].forEach(function(tick) {
        	    d3.select(tick)
        			.attr("id", function(d,i) {
        				return "label_" + d3.time.month.floor(d).getTime();
        			})
        			.on("mouseover", function(tick) {
        				// extract the datapoint from dataset that is associated with x-axis label
        				var floor_month = d3.time.month.floor(tick).getTime();
        				var d = dataset.filter( function(d) { return d.month.getTime() === floor_month; })[0];
        				highlight_bar("#bar_" + floor_month);
        				highlight_label("#label_" + floor_month);
        				show_tooltip(d);
        			})
        	        .on("mouseout", function(tick) {
        				var floor_month = d3.time.month.floor(tick).getTime();
        				unhighlight_bar("#bar_" + floor_month);
        				unhighlight_label("#label_" + floor_month);
        				hide_tooltip(tick);
        			});
        		});
        };

        function show_tooltip(d) {

            var bar_width_px = bar_width * get_zoom_scale();

            // get the width of the modal. Need for tooltip x-position.
            var modal_width = d3.select("#metric-modal")
                .style('width')
                .slice(0, -2);
            var modal_width = Math.round(Number(modal_width));

            d3.select(".metric_tooltip")
                .html("<b>" + display_date_format(d.month) + "</b><br/>"  + d.count + " " + convert_metric_name(d.count))
                .style("left", (x(d.month) + (modal_width-(width + margin.left + margin.right)) + (bar_width_px/2) - (tooltip_width/2) + "px"))//) + 300 + ((width/dataset.length) * 0.5 * get_zoom_scale())) + "px")
                .style("top", (y(d.count) + 19) + "px");

            d3.select(".metric_tooltip")
                .transition()
        		.duration(60)
                .style("opacity", 0.98);

        };

        function hide_tooltip(d) {

            d3.select(".metric_tooltip")
                .transition()
                .duration(60)
                .style("opacity", 0);
        };


        /*	------------------------------------------------------
        		TICK FORMATTING FUNCTIONS (focus x-axis)
        	------------------------------------------------------  */


        function generate_ticks(t0, t1, dt)  {

            var label_size_px = 45;
            var max_total_labels = Math.floor(width / label_size_px);
            // offset so that labels are at the center of each month.
        	var offset = (day_in_ms*30*bar_width_factor)/2;

            function step(date, next_step)  {
                date.setMonth(date.getMonth() + next_step);
            }

            var time = d3.time.month.floor(t0),
        		time = new Date(time.getTime() + offset),
        		times = [],
        		monthFactors = [1,3,4,12];

            while (time < t1) { times.push(new Date(+time)), step(time, 1)};

            var timesCopy = times;
            var i;

            for(i=0 ; times.length > max_total_labels ; i++){
                var times = _.filter(timesCopy, function(d){ return (d.getMonth()) % monthFactors[i] == 0; } )
        	};

            return times;

        };

        function format_months(d){
        	add_tick_behaviour(); // add tick hover behaviour everytime ticks are re-formatted;
        	var test = (x.domain()[1] - x.domain()[0]) > 132167493818; // when to switch from yyyy to mm-yyyy
        	if(d.getMonth()==0 & test){//if january
        		var yearOnly = d3.time.format("%Y");
        		return(yearOnly(d));
        	} else {
        		return(display_date_format(d))
        	}
        }

        /*	------------------------------------------------------
        		BRUSH & ZOOM BEHAVIOUR
        	------------------------------------------------------  */

        function change_focus_brush() {
        	// make the x domain match the brush domain
            x.domain(brush.empty() ? x_context.domain() : brush.extent());
        	// reset zoom
            zoom.x(x);
        	// re-draw axis and elements at new scale
        	update_focus();
        	// update the explanatory text (total views, date range)
            update_context();
        }

        function change_focus_zoom() {
            // make the brush range change with the x domain in focus
            brush.extent(x.domain());
            vis.select(".brush").call(brush);
        	// re-draw axis and elements at new scale
        	update_focus();
            // update the explanatory text (total views, date range)
            update_context();
        }

        function update_focus() {

            // calculate where the bar goes out of focus
            var bar_width_days = bar_width_factor*30.5;

        	var left_date = x.domain()[0];
        	if(left_date.getDate() < bar_width_days){
        		var left_date = d3.time.month.floor(left_date),
        			left_date = new Date(left_date.getTime())
        	};

        	var data_subset_focus = dataset.filter( function(d) {
        		return d.month <= x.domain()[1] && d.month >= left_date
        	});

        	var y_max_focus = d3.max(data_subset_focus, function(d) { return d.count; }) * 1.04 || 1.04;
        	var y_change_duration = 85;

        	// reset y-axis
        	y.domain([0, y_max_focus]);
        	focus.select(".y.axis")
        		.transition()
        		.duration(y_change_duration*0.95)
        		.call(y_axis);

        	// reset bar height given y-axis
        	focus.selectAll(".bar")
        		.transition()
        		.duration(y_change_duration)
        		.attr("y", function (d) {return y(d.count);	  		})
        		.attr("height", function (d) {return y(0) - y(d.count);	  		});

        	// redraw other elements
        	focus.select(".x.axis").call(x_axis);
        	focus.selectAll(".bar")
        		.attr("x", function (d) {return x(d.month); })
        		.attr("width", bar_width * get_zoom_scale())
        		.style("opacity", "1"); // incase user scrolls before entrance animation finishes.

        };

        function update_context() {

        // updates display dates, total count, and decreases opacity of context bars out of focus
            var b = brush.extent();

        	// calculate where the bar goes out of focus
            var bar_width_days = bar_width_factor*30.5;
        	if(b[0].getDate() >= bar_width_days){
        		var left_date = d3.time.month.ceil(b[0]),
        			left_date = new Date(left_date.getTime())
        	} else {
        		left_date = d3.time.month.floor(b[0])
        	};

            // get the range of data in focus
            // if there's only one data point, make sure start and end month are the same
            if (metricMonths_parsed.length == 1) {
                var start_month = display_date_format(new Date(metricMonths_parsed[0])),
                    end_month   = start_month;
            } else {
                var start_month = (brush.empty()) ? display_date_format(x_full_extent[0]) : display_date_format(left_date),
                    end_month   = (brush.empty()) ? display_date_format(x_full_extent[1]) : display_date_format(b[1]);
            };

        	var data_subset_focus = dataset.filter(function(d) {
                if (metricMonths_parsed.length == 1) {
                    return d.month
                }
                else {
                    return d.month <= display_date_format.parse(end_month) && d.month >= left_date
                };
        	});

        	// calcualte the total views/downloads within focus area
        	var total_count = 0;
            for (var i = 0; i < data_subset_focus.length; i++) {
                    total_count += data_subset_focus[i].count;
            }

            // Update start and end dates and total count
            vis.select("#displayDates")
                .text(start_month == end_month ? "in " + start_month : "from " + start_month + " to " + end_month);
        	vis.select("#totalCount")
        		.text(total_count + " " + convert_metric_name(total_count));

        	// Fade all years in the bar chart not within the brush
            context.selectAll(".bar_context")
        		.style("opacity", function(d, i) {

                    if (metricMonths_parsed.length == 1) {
                        return "1";
                    } else {
                        return  d.month <= display_date_format.parse(end_month) && d.month >= left_date || brush.empty() ? "1" : ".3";
                    }

            });

        };

        function check_bounds() {
        // when brush stops moving:

            // check whether chart was scrolled out of bounds and fix,
            var b = brush.extent();
            var out_of_bounds = brush.extent().some(function(e) { return e < x_full_extent[0] | e > x_full_extent[1]; });
            if (out_of_bounds){ b = move_in_bounds(b) };

        };

        function move_in_bounds(b) {
        // move back to boundaries if user pans outside min and max date.

            var year_in_ms = 31536000000,
                brush_start_new,
                brush_end_new;

            if       (b[0] < x_full_extent[0])   { brush_start_new = x_full_extent[0]; }
            else if  (b[0] > x_full_extent[1])   { brush_start_new = x_full_extent[0]; }
            else                        { brush_start_new = b[0]; };

            if       (b[1] > x_full_extent[1])   { brush_end_new = x_full_extent[1]; }
            else if  (b[1] < x_full_extent[0])   { brush_end_new = x_full_extent[1]; }
            else                        { brush_end_new = b[1]; };

            brush.extent([brush_start_new, brush_end_new]);

            brush(d3.select(".brush").transition());
            change_focus_brush();
            change_focus_zoom();

            return(brush.extent())
        };

        function zoom_to_interval(d,i) {
        // action for buttons that zoom focus to certain time interval

            var b = brush.extent(),
                interval_ms,
                brush_end_new,
                brush_start_new;

            if      (d == "year")   { interval_ms = 31536000000}
            else if (d == "month")  { interval_ms = 2592000000 };

            if ( d == "year" | d == "month" )  {

                if((x_full_extent[1].getTime() - b[1].getTime()) < interval_ms){
                // if brush is too far to the right that increasing the right-hand brush boundary would make the chart go out of bounds....
                    brush_start_new = new Date(x_full_extent[1].getTime() - interval_ms); // ...then decrease the left-hand brush boundary...
                    brush_end_new = x_full_extent[1]; //...and set the right-hand brush boundary to the maxiumum limit.
                } else {
                // otherwise, increase the right-hand brush boundary.
                    brush_start_new = b[0];
                    brush_end_new = new Date(b[0].getTime() + interval_ms);
                };

            } else if ( d == "all")  {
                brush_start_new = x_full_extent[0];
                brush_end_new = x_full_extent[1]
            } else {
                brush_start_new = b[0];
                brush_end_new = b[1];
            };

            brush.extent([brush_start_new, brush_end_new]);

            // now draw the brush to match our extent
            brush(d3.select(".brush").transition());
            // now fire the brushstart, brushmove, and check_bounds events
            brush.event(d3.select(".brush").transition());
        };

        // that's it!
    }
        return this;

    }

    });

    return MetricsChartView;

});