This is a follow on from a simple line graph and is based on @mbostock’s example here.
It impliments a simple tooltip which I find particularly neat. This implimentation is designed as a simple example which will be built on to create a slightly more complex example.
This graph is part of the code samples for the update to the book D3 Tips and Tricks to version 6 of d3.js.
<!DOCTYPE html>
<meta charset="utf-8">
<style> /* set the CSS */
.line {
fill: none;
stroke: steelblue;
stroke-width: 2px;
}
</style>
<body>
<!-- load the d3.js library -->
<script src="https://d3js.org/d3.v6.min.js"></script>
<script>
// set the dimensions and margins of the graph
var margin = {top: 20, right: 20, bottom: 30, left: 50},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
// parse the date / time
var parseTime = d3.timeParse("%d-%b-%y");
bisectDate = d3.bisector(function(d) { return d.date; }).left;
// set the ranges
var x = d3.scaleTime().range([0, width]);
var y = d3.scaleLinear().range([height, 0]);
// define the line
var valueline = d3.line()
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.close); });
// append the svg obgect to the body of the page
// appends a 'group' element to 'svg'
// moves the 'group' element to the top left margin
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").then(function(data) {
// format the data
data.forEach(function(d) {
d.date = parseTime(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")
.data([data])
.attr("class", "line")
.attr("d", valueline);
// Add the X Axis
svg.append("g")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
// Add the Y Axis
svg.append("g")
.call(d3.axisLeft(y));
// append the circle at the intersection
focus.append("circle")
.attr("class", "y")
.style("fill", "none")
.style("stroke", "blue")
.attr("r", 4);
// 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.pointer(event,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) + ")");
}
});
</script>
</body>
date,close
26-Mar-12,606.98
27-Mar-12,614.48
28-Mar-12,617.62
29-Mar-12,609.86
30-Mar-12,599.55
2-Apr-12,618.63
3-Apr-12,629.32
4-Apr-12,624.31
5-Apr-12,633.68
9-Apr-12,636.23
10-Apr-12,628.44
11-Apr-12,626.20
12-Apr-12,622.77
13-Apr-12,605.23
16-Apr-12,580.13
17-Apr-12,543.70
18-Apr-12,443.34
19-Apr-12,345.44
20-Apr-12,234.98
23-Apr-12,166.70
24-Apr-12,130.28
25-Apr-12,99.00
26-Apr-12,89.70
27-Apr-12,67.00
30-Apr-12,53.98
1-May-12,58.13
date,close
1-May-12,58.13
30-Apr-12,53.98
27-Apr-12,67.00
26-Apr-12,89.70
25-Apr-12,99.00
24-Apr-12,130.28
23-Apr-12,166.70
20-Apr-12,234.98
19-Apr-12,345.44
18-Apr-12,443.34
17-Apr-12,543.70
16-Apr-12,580.13
13-Apr-12,605.23
12-Apr-12,622.77
11-Apr-12,626.20
10-Apr-12,628.44
9-Apr-12,636.23
5-Apr-12,633.68
4-Apr-12,624.31
3-Apr-12,629.32
2-Apr-12,618.63
30-Mar-12,599.55
29-Mar-12,609.86
28-Mar-12,617.62
27-Mar-12,614.48
26-Mar-12,606.98