Scatterplot with Lasso on points

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.dot {
  stroke: #000;
}

.lasso path {
  stroke: rgb(80,80,80);
  stroke-width:2px;
}

.lasso .drawn {
  fill-opacity:.05 ;
}

.lasso .loop_close {
  fill:none;
  stroke-dasharray: 4,4;
}

.lasso .origin {
  fill:#3399FF;
  fill-opacity:.5;
}

.not_possible {
  fill:rgb(200,200,200);
}

.possible {
  fill:#EC888C;
}

svg {
  margin-left: 30px;
  margin-top: 30px;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src = "lasso.js"></script>
<script>

var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var x = d3.scale.linear()
    .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 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 + ")");

// Create the area where the lasso event can be triggered
svg.append("rect")
  .attr('class','lassoable')
  .attr("width",width)
  .attr("height",height)
  .style("opacity",0);

// Lasso functions to execute while lassoing
var lasso_start = function() {
  lasso.items()
    .attr("r",3.5) // reset size
    .style("fill",null) // clear all of the fills
    .classed({"not_possible":true,"selected":false}); // style as not possible
};

var lasso_draw = function() {
  // Style the possible dots
  lasso.items().filter(function(d) {return d.possible===true})
    .classed({"not_possible":false,"possible":true});

// Style the not possible dot
  lasso.items().filter(function(d) {return d.possible===false})
    .classed({"not_possible":true,"possible":false});
};

var lasso_end = function() {
  // Reset the color of all dots
  lasso.items()
     .style("fill", function(d) { return color(d.species); });

// Style the selected dots
  lasso.items().filter(function(d) {return d.selected===true})
    .classed({"not_possible":false,"possible":false})
    .attr("r",7);

// Reset the style of the not selected dots
  lasso.items().filter(function(d) {return d.selected===false})
    .classed({"not_possible":false,"possible":false})
    .attr("r",3.5);

};

// Define the lasso
var lasso = d3.lasso()
      .closePathDistance(75) // max distance for the lasso loop to be closed
      .closePathSelect(true) // can items be selected by closing the path?
      .hoverSelect(true) // can items by selected by hovering over them?
      .on("start",lasso_start) // lasso start function
      .on("draw",lasso_draw) // lasso draw function
      .on("end",lasso_end); // lasso end function

d3.tsv("data.tsv", function(error, data) {
  data.forEach(function(d) {
    d.sepalLength = +d.sepalLength;
    d.sepalWidth = +d.sepalWidth;
  });

x.domain(d3.extent(data, function(d) { return d.sepalWidth; })).nice();
  y.domain(d3.extent(data, function(d) { return d.sepalLength; })).nice();

svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis)
    .append("text")
      .attr("class", "label")
      .attr("x", width)
      .attr("y", -6)
      .style("text-anchor", "end")
      .text("Sepal Width (cm)");

svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
    .append("text")
      .attr("class", "label")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Sepal Length (cm)")

var dot_g = svg.append('g')
    .attr('class','lassoable');

dot_g.selectAll(".dot")
      .data(data)
    .enter().append("circle")
      .attr("id",function(d,i) {return "dot_" + i;}) // added
      .attr("class", "dot")
      .attr("r", 3.5)
      .attr("cx", function(d) { return x(d.sepalWidth); })
      .attr("cy", function(d) { return y(d.sepalLength); })
      .style("fill", function(d) { return color(d.species); });

lasso.items(d3.selectAll(".dot"));
  //lasso.items(d3.selectAll("#dot_118"));

var legend = svg.selectAll(".legend")
      .data(color.domain())
    .enter().append("g")
      .attr("class", "legend")
      .attr("transform", function(d, i) { return "translate(0," + i * 20 + ")"; });

legend.append("rect")
      .attr("x", width - 18)
      .attr("width", 18)
      .attr("height", 18)
      .style("fill", color);

legend.append("text")
      .attr("x", width - 24)
      .attr("y", 9)
      .attr("dy", ".35em")
      .style("text-anchor", "end")
      .text(function(d) { return d; });

lasso.area(svg.selectAll('.lassoable'));
  // Init the lasso on the svg:g that contains the dots
  svg.call(lasso);

});

</script>

Modified http://d3js.org/d3.v3.min.js to a secure url

https://d3js.org/d3.v3.min.js