Multiseries line chart with mouseover tooltip

Question

I've created a multi-series line chart using this bl.ocks.org code example. I've managed to recreate it on JSFiddle.

Now, I'm trying to add an x-value mouseover tooltip, which displays the a tooltip at each line when you hover its vertical position. Something like this, but for multiple lines.

I found this StackOverflow answer (it includes a JSFiddle), but I can't seem to make it work with my multiseries line chart.

svg.append("path") // this is the black vertical line to follow mouse
  .attr("class","mouseLine")  
  .style("stroke","black")
  .style("stroke-width", "1px")
  .style("opacity", "0");

var mouseCircle = causation.append("g") // for each line, add group to hold text and circle
      .attr("class","mouseCircle"); 

mouseCircle.append("circle") // add a circle to follow along path
  .attr("r", 7)
  .style("stroke", function(d) { console.log(d); return color(d.key); })
  .style("fill","none")
  .style("stroke-width", "1px"); 

mouseCircle.append("text")
  .attr("transform", "translate(10,3)"); // text to hold coordinates

var bisect = d3.bisector(function(d) { return d.YEAR; }).right; // reusable bisect to find points before/after line

svg.append('svg:rect') // append a rect to catch mouse movements on canvas
  .attr('width', width) // can't catch mouse events on a g element
  .attr('height', height)
  .attr('fill', 'none')
  .attr('pointer-events', 'all')
  .on('mouseout', function(){ // on mouse out hide line, circles and text
        d3.select(".mouseLine")
            .style("opacity", "0");
        d3.selectAll(".mouseCircle circle")
            .style("opacity", "0");
      d3.selectAll(".mouseCircle text")
            .style("opacity", "0");
  })
  .on('mouseover', function(){ // on mouse in show line, circles and text
        d3.select(".mouseLine")
            .style("opacity", "1");
         d3.selectAll(".mouseCircle circle")
            .style("opacity", "1");
        d3.selectAll(".mouseCircle text")
            .style("opacity", "1");
  })
  .on('mousemove', function() { // mouse moving over canvas
      d3.select(".mouseLine")
      .attr("d", function(){
          yRange = y.range(); // range of y axis
          var xCoor = d3.mouse(this)[0]; // mouse position in x
          var xDate = x.invert(xCoor); // date corresponding to mouse x 
          d3.selectAll('.mouseCircle') // for each circle group
              .each(function(d,i){
                 var rightIdx = bisect(data[1].values, xDate); // find date in data that right off mouse
                 var interSect = get_line_intersection(xCoor,  // get the intersection of our vertical line and the data line
                      yRange[0], 
                      xCoor, 
                      yRange[1],
                      x(data[i].values[rightIdx-1].YEAR),
                      y(data[i].values[rightIdx-1].VALUE),
                      x(data[i].values[rightIdx].YEAR),
                      y(data[i].values[rightIdx].VALUE));

              d3.select(this) // move the circle to intersection
                  .attr('transform', 'translate(' + interSect.x + ',' + interSect.y + ')');

              d3.select(this.children[1]) // write coordinates out
                  .text(xDate.toLocaleDateString() + "," + y.invert(interSect.y).toFixed(0));

              });

          return "M"+ xCoor +"," + yRange[0] + "L" + xCoor + "," + yRange[1]; // position vertical line
      });
  });

// from here: https://stackoverflow.com/a/1968345/16363
function get_line_intersection(p0_x, p0_y, p1_x, p1_y, 
    p2_x, p2_y, p3_x, p3_y)
{
    var rV = {};
    var s1_x, s1_y, s2_x, s2_y;
    s1_x = p1_x - p0_x;     s1_y = p1_y - p0_y;
    s2_x = p3_x - p2_x;     s2_y = p3_y - p2_y;

    var s, t;
    s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / (-s2_x * s1_y + s1_x * s2_y);
    t = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / (-s2_x * s1_y + s1_x * s2_y);

    if (s >= 0 && s <= 1 && t >= 0 && t <= 1)
    {
        // Collision detected
        rV.x = p0_x + (t * s1_x);
        rV.y = p0_y + (t * s1_y);
    }

    return rV;
}

So, to put it simply, I want to combine my line chart JSFiddle with this tooltip JSFiddle. Does anybody know how to do this? Or is there an easier way to create a tooltip like this? Any help is appreciated!

Answer 1

The question you referenced I answered back in April. Since then, I've learned a bit more about SVG and d3, so I'll let this serve as an update to that answer.

Note, I borrowed a bit of code from @Duopixel's excellent code sample here.

Here's the commented particulars:

// append a g for all the mouse over nonsense
var mouseG = svg.append("g")
  .attr("class", "mouse-over-effects");

// this is the vertical line
mouseG.append("path")
  .attr("class", "mouse-line")
  .style("stroke", "black")
  .style("stroke-width", "1px")
  .style("opacity", "0");

// keep a reference to all our lines
var lines = document.getElementsByClassName('line');

// here's a g for each circle and text on the line
var mousePerLine = mouseG.selectAll('.mouse-per-line')
  .data(cities)
  .enter()
  .append("g")
  .attr("class", "mouse-per-line");

// the circle
mousePerLine.append("circle")
  .attr("r", 7)
  .style("stroke", function(d) {
    return color(d.name);
  })
  .style("fill", "none")
  .style("stroke-width", "1px")
  .style("opacity", "0");

// the text
mousePerLine.append("text")
  .attr("transform", "translate(10,3)");

// rect to capture mouse movements
mouseG.append('svg:rect')
  .attr('width', width)
  .attr('height', height)
  .attr('fill', 'none')
  .attr('pointer-events', 'all')
  .on('mouseout', function() { // on mouse out hide line, circles and text
    d3.select(".mouse-line")
      .style("opacity", "0");
    d3.selectAll(".mouse-per-line circle")
      .style("opacity", "0");
    d3.selectAll(".mouse-per-line text")
      .style("opacity", "0");
  })
  .on('mouseover', function() { // on mouse in show line, circles and text
    d3.select(".mouse-line")
      .style("opacity", "1");
    d3.selectAll(".mouse-per-line circle")
      .style("opacity", "1");
    d3.selectAll(".mouse-per-line text")
      .style("opacity", "1");
  })
  .on('mousemove', function() { // mouse moving over canvas
    var mouse = d3.mouse(this);

    // move the vertical line
    d3.select(".mouse-line")
      .attr("d", function() {
        var d = "M" + mouse[0] + "," + height;
        d += " " + mouse[0] + "," + 0;
        return d;
      });

    // position the circle and text
    d3.selectAll(".mouse-per-line")
      .attr("transform", function(d, i) {
        console.log(width/mouse[0])
        var xDate = x.invert(mouse[0]),
            bisect = d3.bisector(function(d) { return d.date; }).right;
            idx = bisect(d.values, xDate);

        // since we are use curve fitting we can't relay on finding the points like I had done in my last answer
        // this conducts a search using some SVG path functions
        // to find the correct position on the line
        // from http://bl.ocks.org/duopixel/3824661
        var beginning = 0,
            end = lines[i].getTotalLength(),
            target = null;

        while (true){
          target = Math.floor((beginning + end) / 2);
          pos = lines[i].getPointAtLength(target);
          if ((target === end || target === beginning) && pos.x !== mouse[0]) {
              break;
          }
          if (pos.x > mouse[0])      end = target;
          else if (pos.x < mouse[0]) beginning = target;
          else break; //position found
        }

        // update the text with y value
        d3.select(this).select('text')
          .text(y.invert(pos.y).toFixed(2));

        // return position
        return "translate(" + mouse[0] + "," + pos.y +")";
      });
  });

---

Full working code:

<!DOCTYPE html>
<html>

<head>
  <script data-require="d3@3.5.3" data-semver="3.5.3" src="//cdnjs.cloudflare.com/ajax/libs/d3/3.5.3/d3.js"></script>
  <style>
    body {
      font: 10px sans-serif;
    }
    
    .axis path,
    .axis line {
      fill: none;
      stroke: #000;
      shape-rendering: crispEdges;
    }
    
    .x.axis path {
      display: none;
    }
    
    .line {
      fill: none;
      stroke: steelblue;
      stroke-width: 1.5px;
    }
  </style>
</head>

<body>
  <script>
    var myData = "date New York San Francisco Austin\n\
20111001 63.4 62.7 72.2\n\
20111002 58.0 59.9 67.7\n\
20111003 53.3 59.1 69.4\n\
20111004 55.7 58.8 68.0\n\
20111005 64.2 58.7 72.4\n\
20111006 58.8 57.0 77.0\n\
20111007 57.9 56.7 82.3\n\
20111008 61.8 56.8 78.9\n\
20111009 69.3 56.7 68.8\n\
20111010 71.2 60.1 68.7\n\
20111011 68.7 61.1 70.3\n\
20111012 61.8 61.5 75.3\n\
20111013 63.0 64.3 76.6\n\
20111014 66.9 67.1 66.6\n\
20111015 61.7 64.6 68.0\n\
20111016 61.8 61.6 70.6\n\
20111017 62.8 61.1 71.1\n\
20111018 60.8 59.2 70.0\n\
20111019 62.1 58.9 61.6\n\
20111020 65.1 57.2 57.4\n\
20111021 55.6 56.4 64.3\n\
20111022 54.4 60.7 72.4\n";

    var margin = {
        top: 20,
        right: 80,
        bottom: 30,
        left: 50
      },
      width = 500 - margin.left - margin.right,
      height = 500 - margin.top - margin.bottom;

    var parseDate = d3.time.format("%Y%m%d").parse;

    var x = d3.time.scale()
      .range([0, width]);

    var y = d3.scale.linear()
      .range([height, 0]);

    var color = d3.scale.category10();

    var xAxis = d3.svg.axis()
      .scale(x)
      .orient("bottom");

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

    var line = d3.svg.line()
      .interpolate("basis")
      .x(function(d) {
        return x(d.date);
      })
      .y(function(d) {
        return y(d.temperature);
      });

    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 data = d3.tsv.parse(myData);

    color.domain(d3.keys(data[0]).filter(function(key) {
      return key !== "date";
    }));

    data.forEach(function(d) {
      d.date = parseDate(d.date);
    });

    var cities = color.domain().map(function(name) {
      return {
        name: name,
        values: data.map(function(d) {
          return {
            date: d.date,
            temperature: +d[name]
          };
        })
      };
    });

    x.domain(d3.extent(data, function(d) {
      return d.date;
    }));

    y.domain([
      d3.min(cities, function(c) {
        return d3.min(c.values, function(v) {
          return v.temperature;
        });
      }),
      d3.max(cities, function(c) {
        return d3.max(c.values, function(v) {
          return v.temperature;
        });
      })
    ]);

    var legend = svg.selectAll('g')
      .data(cities)
      .enter()
      .append('g')
      .attr('class', 'legend');

    legend.append('rect')
      .attr('x', width - 20)
      .attr('y', function(d, i) {
        return i * 20;
      })
      .attr('width', 10)
      .attr('height', 10)
      .style('fill', function(d) {
        return color(d.name);
      });

    legend.append('text')
      .attr('x', width - 8)
      .attr('y', function(d, i) {
        return (i * 20) + 9;
      })
      .text(function(d) {
        return d.name;
      });

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

    svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
      .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Temperature (ºF)");

    var city = svg.selectAll(".city")
      .data(cities)
      .enter().append("g")
      .attr("class", "city");

    city.append("path")
      .attr("class", "line")
      .attr("d", function(d) {
        return line(d.values);
      })
      .style("stroke", function(d) {
        return color(d.name);
      });

    city.append("text")
      .datum(function(d) {
        return {
          name: d.name,
          value: d.values[d.values.length - 1]
        };
      })
      .attr("transform", function(d) {
        return "translate(" + x(d.value.date) + "," + y(d.value.temperature) + ")";
      })
      .attr("x", 3)
      .attr("dy", ".35em")
      .text(function(d) {
        return d.name;
      });

    var mouseG = svg.append("g")
      .attr("class", "mouse-over-effects");

    mouseG.append("path") // this is the black vertical line to follow mouse
      .attr("class", "mouse-line")
      .style("stroke", "black")
      .style("stroke-width", "1px")
      .style("opacity", "0");
      
    var lines = document.getElementsByClassName('line');

    var mousePerLine = mouseG.selectAll('.mouse-per-line')
      .data(cities)
      .enter()
      .append("g")
      .attr("class", "mouse-per-line");

    mousePerLine.append("circle")
      .attr("r", 7)
      .style("stroke", function(d) {
        return color(d.name);
      })
      .style("fill", "none")
      .style("stroke-width", "1px")
      .style("opacity", "0");

    mousePerLine.append("text")
      .attr("transform", "translate(10,3)");

    mouseG.append('svg:rect') // append a rect to catch mouse movements on canvas
      .attr('width', width) // can't catch mouse events on a g element
      .attr('height', height)
      .attr('fill', 'none')
      .attr('pointer-events', 'all')
      .on('mouseout', function() { // on mouse out hide line, circles and text
        d3.select(".mouse-line")
          .style("opacity", "0");
        d3.selectAll(".mouse-per-line circle")
          .style("opacity", "0");
        d3.selectAll(".mouse-per-line text")
          .style("opacity", "0");
      })
      .on('mouseover', function() { // on mouse in show line, circles and text
        d3.select(".mouse-line")
          .style("opacity", "1");
        d3.selectAll(".mouse-per-line circle")
          .style("opacity", "1");
        d3.selectAll(".mouse-per-line text")
          .style("opacity", "1");
      })
      .on('mousemove', function() { // mouse moving over canvas
        var mouse = d3.mouse(this);
        d3.select(".mouse-line")
          .attr("d", function() {
            var d = "M" + mouse[0] + "," + height;
            d += " " + mouse[0] + "," + 0;
            return d;
          });

        d3.selectAll(".mouse-per-line")
          .attr("transform", function(d, i) {
            console.log(width/mouse[0])
            var xDate = x.invert(mouse[0]),
                bisect = d3.bisector(function(d) { return d.date; }).right;
                idx = bisect(d.values, xDate);
            
            var beginning = 0,
                end = lines[i].getTotalLength(),
                target = null;

            while (true){
              target = Math.floor((beginning + end) / 2);
              pos = lines[i].getPointAtLength(target);
              if ((target === end || target === beginning) && pos.x !== mouse[0]) {
                  break;
              }
              if (pos.x > mouse[0])      end = target;
              else if (pos.x < mouse[0]) beginning = target;
              else break; //position found
            }
            
            d3.select(this).select('text')
              .text(y.invert(pos.y).toFixed(2));
              
            return "translate(" + mouse[0] + "," + pos.y +")";
          });
      });
      
  </script>
</body>

</html>