Scatterplot with Lasso

This example demonstrates incorporating the d3 lasso plugin with a d3 scatterplot. Clicking and dragging on the plot area will produce a lasso that can be used to hover or loop around the dots in the scatterplot. Functions are then executed based on whether dots were selected or not.

The lasso plugin can be found here.

<!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;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src = "https://axc.net/code_libraries/lasso/lasso.min.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 + ")");

// 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);

};

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

// 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?
      .area(lasso_area) // area where the lasso can be started
      .on("start",lasso_start) // lasso start function
      .on("draw",lasso_draw) // lasso draw function
      .on("end",lasso_end); // lasso end function

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

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)")

svg.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"));

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; });

});

</script>

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

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