Favorite tooltip (complex version)

This is a follow on from the favorite simple tooltip graph used as an example in the book D3 Tips and Tricks.

It impliments a more complex example than the simple version and is designed to illustrate additional things you can do with the technique. It should be taken in context with the text of the book which can be downloaded for free from Leanpub.

<!DOCTYPE html>
<meta charset="utf-8">
<style> /* set the CSS */

body { font: 12px Arial;}

path { 
    stroke: steelblue;
    stroke-width: 2;
    fill: none;
}

.axis path,
.axis line {
    fill: none;
    stroke: grey;
    stroke-width: 1;
    shape-rendering: crispEdges;
}

</style>
<body>

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>

// Set the dimensions of the canvas / graph
var margin = {top: 30, right: 20, bottom: 30, left: 50},
    width = 600 - margin.left - margin.right,
    height = 270 - margin.top - margin.bottom;

// Parse the date / time
var parseDate = d3.time.format("%d-%b-%y").parse,
    formatDate = d3.time.format("%d-%b"),
    bisectDate = d3.bisector(function(d) { return d.date; }).left;

// Set the ranges
var x = d3.time.scale().range([0, width]);
var y = d3.scale.linear().range([height, 0]);

// Define the axes
var xAxis = d3.svg.axis().scale(x)
    .orient("bottom").ticks(5);

var yAxis = d3.svg.axis().scale(y)
    .orient("left").ticks(5);

// Define the line
var valueline = d3.svg.line()
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.close); });
    
// Adds the svg canvas
var svg = d3.select("body")
    .append("svg")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom)
    .append("g")
        .attr("transform", 
              "translate(" + margin.left + "," + margin.top + ")");

var lineSvg = svg.append("g");

var focus = svg.append("g") 
    .style("display", "none");

// Get the data
d3.csv("atad.csv", function(error, data) {
    data.forEach(function(d) {
        d.date = parseDate(d.date);
        d.close = +d.close;
    });

// Scale the range of the data
    x.domain(d3.extent(data, function(d) { return d.date; }));
    y.domain([0, d3.max(data, function(d) { return d.close; })]);

// Add the valueline path.
    lineSvg.append("path")
        .attr("class", "line")
        .attr("d", valueline(data));

// Add the X Axis
    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);

// Add the Y Axis
    svg.append("g")
        .attr("class", "y axis")
        .call(yAxis);

// append the x line
    focus.append("line")
        .attr("class", "x")
        .style("stroke", "blue")
        .style("stroke-dasharray", "3,3")
        .style("opacity", 0.5)
        .attr("y1", 0)
        .attr("y2", height);

// append the y line
    focus.append("line")
        .attr("class", "y")
        .style("stroke", "blue")
        .style("stroke-dasharray", "3,3")
        .style("opacity", 0.5)
        .attr("x1", width)
        .attr("x2", width);

// append the circle at the intersection
    focus.append("circle")
        .attr("class", "y")
        .style("fill", "none")
        .style("stroke", "blue")
        .attr("r", 4);

// place the value at the intersection
    focus.append("text")
        .attr("class", "y1")
        .style("stroke", "white")
        .style("stroke-width", "3.5px")
        .style("opacity", 0.8)
        .attr("dx", 8)
        .attr("dy", "-.3em");
    focus.append("text")
        .attr("class", "y2")
        .attr("dx", 8)
        .attr("dy", "-.3em");

// place the date at the intersection
    focus.append("text")
        .attr("class", "y3")
        .style("stroke", "white")
        .style("stroke-width", "3.5px")
        .style("opacity", 0.8)
        .attr("dx", 8)
        .attr("dy", "1em");
    focus.append("text")
        .attr("class", "y4")
        .attr("dx", 8)
        .attr("dy", "1em");
    
    // append the rectangle to capture mouse
    svg.append("rect")
        .attr("width", width)
        .attr("height", height)
        .style("fill", "none")
        .style("pointer-events", "all")
        .on("mouseover", function() { focus.style("display", null); })
        .on("mouseout", function() { focus.style("display", "none"); })
        .on("mousemove", mousemove);

function mousemove() {
		var x0 = x.invert(d3.mouse(this)[0]),
		    i = bisectDate(data, x0, 1),
		    d0 = data[i - 1],
		    d1 = data[i],
		    d = x0 - d0.date > d1.date - x0 ? d1 : d0;

focus.select("circle.y")
		    .attr("transform",
		          "translate(" + x(d.date) + "," +
		                         y(d.close) + ")");

focus.select("text.y1")
		    .attr("transform",
		          "translate(" + x(d.date) + "," +
		                         y(d.close) + ")")
		    .text(d.close);

focus.select("text.y2")
		    .attr("transform",
		          "translate(" + x(d.date) + "," +
		                         y(d.close) + ")")
		    .text(d.close);

focus.select("text.y3")
		    .attr("transform",
		          "translate(" + x(d.date) + "," +
		                         y(d.close) + ")")
		    .text(formatDate(d.date));

focus.select("text.y4")
		    .attr("transform",
		          "translate(" + x(d.date) + "," +
		                         y(d.close) + ")")
		    .text(formatDate(d.date));

focus.select(".x")
		    .attr("transform",
		          "translate(" + x(d.date) + "," +
		                         y(d.close) + ")")
		               .attr("y2", height - y(d.close));

focus.select(".y")
		    .attr("transform",
		          "translate(" + width * -1 + "," +
		                         y(d.close) + ")")
		               .attr("x2", width + width);
	}

});

</script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js