D3.js折线图工具提示问题

Question

我已经使用d3.js创建了折线图，并在图表中添加了工具提示，在鼠标悬停时会创建一个小圆圈并显示y轴值。到此阶段，一切正常，但问题出在鼠标悬停时显示的圆的位置。

我希望此圆圈显示在线条上方，但始终显示在线条图上方或下方。

所以，我必须发出：

1. 要修复工具提示圆，使其始终位于折线图的直线上？
2. 如何显示定义点之间的点的y值？

.interpolate("basis")由于圈子位置变得混乱，我正在使用生成线。我不知道如何解决此问题，因为我需要.interpolate("basis")在我的代码中。

请任何人在此代码中了解如何解决这些问题：

var data = [{
    x: '1-May-12',
    y: 5
  }, {
    x: '30-Apr-12',
    y: 28
  }, {
    x: '27-Apr-12',
    y: 58
  }, {
    x: '26-Apr-12',
    y: 88
  }, {
    x: '25-Apr-12',
    y: 8
  }, {
    x: '24-Apr-12',
    y: 48
  }, {
    x: '23-Apr-12',
    y: 28
  }, {
    x: '20-Apr-12',
    y: 68
  }, {
    x: '19-Apr-12',
    y: 8
  }, {
    x: '18-Apr-12',
    y: 58
  }, {
    x: '17-Apr-12',
    y: 5
  }, {
    x: '16-Apr-12',
    y: 80
  }, {
    x: '13-Apr-12',
    y: 38
  }],
  width = 1200,
  height = 360,
  margin = {
    top: 30,
    right: 20,
    bottom: 30,
    left: 50
  };
width -= margin.left - margin.right;
height -= margin.top - margin.bottom;
var parseDate = d3.time.format("%d-%b-%y").parse;
var x = d3.time.scale().range([0, width]);
var y = d3.scale.linear().range([height, 0]);
var xAxis = d3.svg.axis().scale(x)
  .orient("bottom").ticks(0).tickSize(0)
  .tickFormat("").outerTickSize(0);

var yAxis = d3.svg.axis().scale(y)
  .orient("left").tickSize(0).ticks(0)
  .tickFormat("");

var svg = d3.select("body")
  .append("svg")
  .attr("width", width + margin.left + margin.right)
  .attr("height", height + margin.top + margin.bottom)
  .attr("class", "bg-color")
  .append("g")
  .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// function for the y grid lines
function make_y_axis() {
  return d3.svg.axis()
    .scale(y)
    .orient("left")
    .ticks(10);
}

// Draw the y Grid lines
svg.append("g")
  .attr("class", "grid")
  .call(make_y_axis()
    .tickSize(-width, 0, 0)
    .tickFormat("")
  );

x.domain(d3.extent(data, function(d) {
  return parseDate(d.x);
}));
y.domain([0, d3.max(data, function(d) {
  return d.y;
})]);

data.sort(function(a, b) {
  return parseDate(a.x) - parseDate(b.x);
});

/*x.domain([parseDate(data[0].x), parseDate(data[data.length - 1].x)]);
y.domain(d3.extent(data, function (d) {
    return d.y;
}));*/

// 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);

// Add the valueline path
svg.append("path")
  .attr("class", "line");

// Define the line
var lineGen = d3.svg.line()
  .x(function(d) {
    return x(parseDate(d.x));
  })
  .y(function(d) {
    return y(d.y);
  })
  .interpolate("basis");

svg.append('path')
  .attr("class", "line")
  .attr('d', lineGen(data));

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

focus.append("circle")
  .attr("r", 4.5);

focus.append("text")
  .attr("x", 9)
  .attr("dy", ".35em");

svg.append("rect")
  .attr("class", "overlay")
  .attr("width", width)
  .attr("height", height)
  .on("mouseover", function() {
    focus.style("display", null);
  })
  .on("mouseout", function() {
    focus.style("display", "none");
  })
  .on("mousemove", mousemove);

var bisectDate = d3.bisector(function(d) {
  return parseDate(d.x);
}).left;

function mousemove() {
  var x0 = x.invert(d3.mouse(this)[0]),
    i = bisectDate(data, x0, 1),
    d0 = data[i - 1],
    d1 = data[i],
    d = x0 - parseDate(d0.x) > parseDate(d1.x) - x0 ? d1 : d0;
  console.log(y(d.y));
  focus.attr("transform", "translate(" + x(parseDate(d.x)) + "," + y(d.y) + ")");
  focus.select("text").text(d.y);
}

.x.axis path {
  display: none;
}

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

.overlay {
  fill: none;
  pointer-events: all;
}

.focus circle {
  fill: none;
  stroke: steelblue;
}

.axis path,
.axis line {
  fill: none;
  stroke: grey;
  stroke-width: 2;
  shape-rendering: crispEdges;
}

.grid .tick {
  stroke: lightgrey;
  stroke-opacity: 0.7;
  shape-rendering: crispEdges;
}

.grid path {
  stroke-width: 0;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>

https://jsfiddle.net/nikunj2512/w5y1q5ds/1/

Answer 1

这个问题不时出现，我可以想到两个解决方案。

解决方案1-您可以解析路径本身并将这些点（和值）显示为工具提示，以保留在拟合路径上。该解决方案的缺点是，取决于d3拟合的方式，您最终会得到额外的点还是稍微错位的点：

// get path
var p = svg.select('.line')
  .attr("d");
// parse it by M coords, L coords and C coords
// build an array of points used in generating the path
var points = p.split(/(?=[LMC])/).map(function(d){
  var fChar = d.slice(0, 1);
  if (fChar === "M" || fChar === "L"){
    return d.slice(1, d.length)
            .split(",")
            .map(function(p){ return +p; });
  } else if (fChar === "C") {
    var s = d.split(",");
    return [+s[s.length - 2], +s[s.length - 1]];
  }
});
// modify the bisect our array of points
var bisectDate = d3.bisector(function(d) {
  return d[0];
}).left;
// modify the mousemove
function mousemove() {
  var x0 = d3.mouse(this)[0],
    i = bisectDate(points, x0, 1) - 1,
    y0 = y.invert(points[i][1]);

  //console.log(y(d.y));
  focus.attr("transform", "translate(" + points[i][0] + "," + points[i][1] + ")");
  focus.select("text").text(y0);
}

解决方案2-只需让您的工具提示完整地遵循此路径即可。对于某些内置的SVG构造，这是一种非常简单的方法：

var path = svg.select('.line').node();
var totLength = path.getTotalLength();
function mousemove() {
  var x0 = d3.mouse(this)[0],
      per = width / x0;
      point = path.getPointAtLength(totLength / per)
      y0 = y.invert(point.y);

  focus.attr("transform", "translate(" + point.x + "," + point.y + ")");
  focus.select("text").text(y0);
}

解决方案1-完整的工作代码：

// get path
var p = svg.select('.line')
  .attr("d");
// parse it by M coords, L coords and C coords
// build an array of points used in generating the path
var points = p.split(/(?=[LMC])/).map(function(d){
  var fChar = d.slice(0, 1);
  if (fChar === "M" || fChar === "L"){
    return d.slice(1, d.length)
            .split(",")
            .map(function(p){ return +p; });
  } else if (fChar === "C") {
    var s = d.split(",");
    return [+s[s.length - 2], +s[s.length - 1]];
  }
});
// modify the bisect our array of points
var bisectDate = d3.bisector(function(d) {
  return d[0];
}).left;
// modify the mousemove
function mousemove() {
  var x0 = d3.mouse(this)[0],
    i = bisectDate(points, x0, 1) - 1,
    y0 = y.invert(points[i][1]);

  //console.log(y(d.y));
  focus.attr("transform", "translate(" + points[i][0] + "," + points[i][1] + ")");
  focus.select("text").text(y0);
}

解决方案2-完整的工作代码：

var path = svg.select('.line').node();
var totLength = path.getTotalLength();
function mousemove() {
  var x0 = d3.mouse(this)[0],
      per = width / x0;
      point = path.getPointAtLength(totLength / per)
      y0 = y.invert(point.y);

  focus.attr("transform", "translate(" + point.x + "," + point.y + ")");
  focus.select("text").text(y0);
}