sparkline.js

function sparkline() {
  var margin = {top: 5, right: 5, bottom: 5, left: 5},
      width = 50,
      height = 20,
      xValue = function(d, i) { return i; },
      yValue = function(d) { return d; },
      xScale = d3.time.scale(),
      yScale = d3.scale.linear(),
      area = d3.svg.area().x(X).y1(Y),
      line = d3.svg.line().x(X).y(Y),
      interpolate = 'linear';

  function chart(selection) {
    selection.each(function(data) {
      // Convert data to standard representation greedily;
      // this is needed for nondeterministic accessors.
      data = data.map(function(d, i) {
        return [xValue.call(data, d, i), yValue.call(data, d, i)];
      });

      line.interpolate(interpolate);
      area.interpolate(interpolate);

      // Update the x-scale.
      xScale
          .domain(d3.extent(data, function(d) { return d[0]; }))
          .range([0, width - margin.left - margin.right]);

      // Update the y-scale.
      yScale
          .domain(d3.extent(data, function(d) { return d[1]; }))
          .range([height - margin.top - margin.bottom, 0]);

      // Select the svg element, if it exists.
      var svg = d3.select(this).selectAll("svg").data([data]);

      // Otherwise, create the skeletal chart.
      var gEnter = svg.enter().append("svg").append("g");
      gEnter.append("path").attr("class", "area");
      gEnter.append("path").attr("class", "line");

      // Update the outer dimensions.
      svg .attr("width", width)
          .attr("height", height);

      // Update the inner dimensions.
      var g = svg.select("g")
          .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

      // Update the area path.
      g.select(".area")
          .attr("d", area.y0(yScale.range()[0]));

      // Update the line path.
      g.select(".line")
          .attr("d", line);
    });
  }


  // The x-accessor for the path generator; xScale ∘ xValue.
  function X(d) {
    return xScale(d[0]);
  }

  // The x-accessor for the path generator; yScale ∘ yValue.
  function Y(d) {
    return yScale(d[1]);
  }

  chart.margin = function(_) {
    if (!arguments.length) return margin;
    margin = _;
    return chart;
  };

  chart.width = function(_) {
    if (!arguments.length) return width;
    width = _;
    return chart;
  };

  chart.height = function(_) {
    if (!arguments.length) return height;
    height = _;
    return chart;
  };

  chart.x = function(_) {
    if (!arguments.length) return xValue;
    xValue = _;
    return chart;
  };

  chart.interpolate = function(_) {
    if (!arguments.length) return interpolate;
    interpolate = _;
    return chart;
  };

  chart.y = function(_) {
    if (!arguments.length) return yValue;
    yValue = _;
    return chart;
  };

  return chart;
}