D3 Examples - D3 v4 Line Chart

D3 v4 Line Chart
D3 v4 Line Chart Example
This is a example for basic line chart using D3. We are using the newest version of D3, version 4. As for all visualizations, we can break down this work into a checklist.
Line Chart Checklist
Add an SVG to draw our line chart on
Use the D3 standard margin convetion
Create an x axis
Create a y axis
Create an x scale
Create a y scale
Create a line generator
Create a random dataset
Create a path object for the line
Bind the data to the path object
Call the line generator on the data-bound path object
Add circles to show each datapoint
Add some basic styling to the chart so its easier on the eyes
Read through the code below to see where each part of the checklist is completed.
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<!DOCTYPE html>
<meta charset="utf-8">
<style type="text/css">
.line {
     fill: none;
     stroke-width: 4;
     stroke-linecap: round;
     stroke-linejoin: bevel;
}
.line.strength {
    stroke: #875D9A;
}
.line.interest {
    stroke: #61D3A5;
}
.line.dashed {
     stroke-dasharray: 10 10;
}
.today {
     stroke-width: 2;
     stroke: #338FFC;
}
.today-text {
     fill: #338FFC;
     font-family: "Helvetica Neue";
     font-size: 14px;
     text-anchor: middle;
}
.center-y {
     stroke-width: 2;
     stroke: #875D9A;
}
.center-text {
     fill: #875D9A;
     font-family: "Helvetica Neue";
     font-size: 14px;
     text-anchor: middle;
}
.tick text {
     font-family: "Helvetica Neue";
     font-size: 16px;
         text-anchor: middle;
}
</style>
<body>
</body>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
// Data
const dataset1 = JSON.parse('[73.76485163027888,88.14314869551498,60.07160491671124,78.05917782144006,92.84690323913051,87.77022060741578,87.65266340207693,52.02965719713634,65.8700937116689,63.143085790431606,77.51285081290519,89.47117627132704,99.27408547811402,87.99858960412732,83.66506795366232,88.53211932576345,99.5094600639527,56.66014023625252,67.6995830391757,63.998180923002366,66.51164077564725,80.16849630600868,55.973509828607725,94.88309818299956,70.24926011032275,89.2774150560498,89.00381706016418,91.0780470510668,82.05933734906436]');
const dataset2 = JSON.parse('[80.73618473493161,88.05885666592522,98.7048816420985,74.79973316682464,67.254335813292,62.44722842133699,83.80271025274195,88.44556972808486,63.0330640574728,85.08327811406141,92.09447015491307,75.88646047806537,60.131218776193876,82.48795809853172,89.45430727528588,97.87417843831301,76.14124806290442,55.89406081061487,91.85792353943552,99.44041241846986,73.81760885821723,63.59228062243233,52.21401593797178,64.1732245543982,70.2075416481421,76.5982175249886,72.04620658856541,62.25888013762293,86.50173611465081]');
const dataset3 = JSON.parse('[11.6309347140356367,35.6430965753907,9.746423099201152,39.98647515573946,17.98027613743821,3.486469410501858,45.072967972773256,43.19067593266349,43.64312238338458,2.6638327695559627,35.49974849768752,37.76264997103447,5.305161811793269,26.743664290160083,28.447241277111203,7.442892296100901,36.07707697281577,9.159932090281785,26.74222560898597,13.918782227917227,33.00857048879784,28.656977770686787,23.286804306942678,39.61776395294071,19.231098301010363,36.82031101548148,14.719176547755753,2.399024152359308,20.279515765680955]');
const dataset4 = JSON.parse('[12.5804864395190799,4.423716487585305,44.38469228742593,22.464681279568754,49.29188761696336,20.831848000831187,22.973913573390824,47.18320458242374,47.720363830206416,26.97593329221013,13.49367755618619,34.250680716061055,41.70916366924611,47.067658950647925,37.06380506433143,43.79930466097505,26.400890061824867,30.64057803574093,29.635152109799357,47.80675224987022,14.875293828279634,2.7155919318852195,14.426866016353923,31.575105367917477,45.194747660107005,29.393420628430455,24.844235497150446,3.6585916851372025,38.88205391627133]');
​
const margin = {
        top: 50,
        right: 0,
        bottom: 50,
        left: 80
    },
    width = window.innerWidth - margin.left - margin.right,
    height = window.innerHeight - margin.top - margin.bottom;
​
const addDays = (date, days) => {
    const d = new Date(date.valueOf());
    d.setDate(d.getDate() + days);
    return d;
}
​
const n = 29;
const firstDate = new Date(2018, 0, 10);
const lastDate = addDays(firstDate, 28);
const todayDate = new Date(2018, 0, 18);
const gridColor = '#8D98A2';
const gridlineColor = '#E7ECF1';
​
// Scales
const xScale = d3.scaleTime()
    .domain([firstDate, lastDate])
    .range([0, width]);
​
const yScale = d3.scaleLinear()
    .domain([0, 100]) // input 
    .range([height, 0]); // output 
​
// Line generator
const line = d3.line()
    .x(function(d, i) {
        return xScale(d.x);
    })
    .y(function(d) {
        return yScale(d.y);
    })
    .curve(d3.curveCatmullRom)
​
const getDataset = (ds) => d3.range(n).map(function(d) {
    return {
        "y": ds[d],
        "x": addDays(firstDate, d)
    }
});
​
const 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 + ")");
​
// X Axis
const formatTimeXSameMonth = d3.timeFormat("%B %e");
const formatTimeX = d3.timeFormat("%b %e");
const formatX = (d) => {
    const left = addDays(d, -3);
    const right = addDays(d, 3);
    if (left.getMonth() === right.getMonth()) {
        return formatTimeXSameMonth(left) + ' - ' + right.getDate()
    } else {
        return formatTimeX(left) + ' - ' + formatTimeX(right)
    }
};
const xAxis = d3.axisBottom(xScale)
    .tickValues([addDays(firstDate, 3),
        addDays(firstDate, 10),
        addDays(firstDate, 17),
        addDays(firstDate, 24)
    ])
    .tickFormat(formatX);
const customX = (g) => {
    g.call(xAxis);
    g.select(".domain").remove();
    g.selectAll('.tick line').remove();
    g.selectAll('.tick text').attr('fill', gridColor)
}
svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(" + (width * 0.02) + "," + (height + 6) + ")")
    .call(customX);
​
const gridlinesXAxis = () => d3.axisBottom(xScale).tickValues([
    addDays(firstDate, 0),
    addDays(firstDate, 7),
    addDays(firstDate, 14),
    addDays(firstDate, 21),
    addDays(firstDate, 28)
]);
const gridlinesX = (g) => {
    g.call(gridlinesXAxis()
        .tickSize(-height - margin.top - 40)
        .tickFormat(""));
    g.select(".domain").remove();
    g.selectAll('.tick text').remove();
    g.selectAll('.tick line').attr('stroke', gridlineColor)
}
svg.append("g")
    .attr("class", "grid")
    .attr("transform", "translate(0," + (height + margin.top - 10) + ")")
    .attr("stroke", gridColor)
    .call(gridlinesX);
​
// Y Axis
const yAxis = d3.axisLeft(yScale)
    .tickValues([0, 25, 50, 75, 100])
    .tickFormat(d => d + '%');
​
const customY = (g) => {
    g.call(yAxis)
    g.select(".domain").remove();
    g.selectAll('.tick line').remove();
    g.selectAll('.tick text').attr('fill', gridColor).attr('x', -43)
}
svg.append("g")
    .attr("class", "y axis")
    .call(customY);
​
const gridlinesYAxis = () => d3.axisRight(yScale).tickValues([0]);
const gridlinesY = (g) => {
    g.call(gridlinesYAxis()
        .tickFormat("")
        .tickSize(width + margin.right + margin.left));
    g.select(".domain").remove();
    g.selectAll('.tick text').remove();
    g.selectAll('.tick line').attr('stroke', gridlineColor)
}
svg.append("g")
    .attr("class", "grid")
    .call(gridlinesY);
​
// Draw line 
const getPastDataset = (ds) => ds.filter(d => d.x <= todayDate);
const getFutureDataset = (ds) => {
  const past = getPastDataset(ds);
  return [past[past.length - 1]].concat(ds.filter(d => d.x > todayDate));
}
​
const useDataset = (dataset, cssClass) => {
    const pastDataset = getPastDataset(dataset);
    const futureDataset = getFutureDataset(dataset);
​
    svg.append("path")
        .attr("class", "line " + cssClass)
        .attr("d", line(pastDataset));
​
    return svg.append("path")
        .attr("class", "line dashed " + cssClass)
        .attr("d", line(futureDataset));
}
​
const interestLine = useDataset(getDataset(dataset1), 'interest');
const strengthLine = useDataset(getDataset(dataset3), 'strength');
​
const animate = (n) => {
    const interestDs = getFutureDataset(getDataset(n === 1 ? dataset1 : dataset2));
    interestLine.transition().ease(d3.easeQuad).duration(1000).attr("d", line(interestDs));
​
    const strengthDs = getFutureDataset(getDataset(n === 1 ? dataset3 : dataset4));
    strengthLine.transition().ease(d3.easeQuad).duration(1000).attr("d", line(strengthDs));
}
​
// Draw today
const todayX = xScale(todayDate);
svg.append("line")
    .attr("x1", todayX)
    .attr("y1", 70 - margin.top)
    .attr("x2", todayX)
    .attr("y2", height)
    .attr("class", "today");
svg.append("line")
    .attr("x1", todayX)
    .attr("y1", -margin.top)
    .attr("x2", todayX)
    .attr("y2", 30 - margin.top)
    .attr("class", "today");
svg.append("text")
    .text('Today')
    .attr("class", "today-text")
    .attr('x', todayX)
    .attr('y', 50 - margin.top)
    .attr('alignment-baseline', 'central');;
​
// Center Y Axis
const centerY = yScale(50);
svg.append("line")
    .attr("x1", 0)
    .attr("y1", centerY)
    .attr("x2", width - 170)
    .attr("y2", centerY)
    .attr("class", "center-y");
svg.append("line")
    .attr("x1", width - 30)
    .attr("y1", centerY)
    .attr("x2", width)
    .attr("y2", centerY)
    .attr("class", "center-y");
svg.append("text")
    .text('HEALTHY TARGET')
    .attr("class", "center-text")
    .attr('x', width - 100)
    .attr('y', centerY)
    .attr('alignment-baseline', 'central');
</script>
​
​
    