IRIS scatterplot and regression

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

body {
  font: 10px sans-serif;
}

.tooltip {
	position: absolute;
	width: 0px;
	height: 28px;
	pointer-events: none;
}
  
.line {
    stroke: #e53100;
    fill: none;
    stroke-width: 3;
}

</style>
<body>
	<script src="https://d3js.org/d3.v4.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.scaleLinear()
    .range([0, width]);

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

var r = d3.scaleSqrt()
		.range([3,10]);
  
var xAxis = d3.axisBottom()
		.scale(x);

var yAxis = d3.axisLeft()
		.scale(y);
  
var color = d3.scaleOrdinal(d3.schemeCategory10);

var symbol = d3.symbol(["circle", "cross", "diamond"]);

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 tooltip = d3.select("body").append("div")
					.attr("class", "tooltip")
					.style("opacity", 0);

d3.csv('https://raw.githubusercontent.com/LyonDataViz/MOS5.5-Dataviz/master/data/iris.csv', function(error, data){
	data.forEach(function(d){
    d.petal_length = +d.petal_length;
    d.petal_width  = +d.petal_width;
	});

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

y.domain(d3.extent(data, function(d){
		return d.petal_width;
	}));

r.domain(d3.extent(data, function(d){
		return d.sepal_length;
	}))();
  
  var path = svg.selectAll("path")
				.data(data)
				.enter()
				.append("path")
  
  path.attr("transform", function(d) { return "translate(" + x(d.petal_length) + ", " + y(d.petal_width) + ")"; })
				.attr("d", d3.symbol()
								.type(function(d){
									if (d.species == 'setosa'){
										return d3.symbolSquare;
									}
									else if (d.species == 'versicolor') {
										return d3.symbolDiamond;
									}
									else if (d.species == 'virginica') {
										return d3.symbolStar;
									}
									
								}))
				.style("fill", function(d){ return color(d.species); })

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

svg.append('g')
    .attr('transform', 'translate(0,0)')
    .attr('class', 'y axis')
    .call(yAxis);

svg.append('text')
		.attr('x', 10)
		.attr('y', 10)
		.attr('class', 'label')
		.text('petal Width');

svg.append('text')
		.attr('x', width)
		.attr('y', height - 10)
		.attr('text-anchor', 'end')
		.attr('class', 'label')
		.text('Petal Length');

svg.selectAll(".dot")
    .data(data)
  .enter().append("circle")
    .attr("class", "dot")
    .attr("r", function(d) { return r(d.petal_length); })
    .attr("cx", function(d) { return x(d.petal_length); })
    .attr("cy", function(d) { return y(d.petal_width); })
    .style("fill", function(d) { return color(d.species); })
    .on("mouseover", function(d){
		   tooltip.transition()
		   	.duration(0)
		   	.style("opacity", .9);
		   tooltip.html("Species:" + d.species)
		   	.style("left", (d3.event.pageX + 5) + "px")
		   	.style("top", (d3.event.pageY - 28) + "px");
		 })
		.on("mouseout", function(d){
			tooltip.transition()
				.duration(500)
				.style("opacity",0);
		});
  
  			// Regression lineaire

var x_mean = d3.mean(data, function(d){ return d.petal_length; });
			var y_mean = d3.mean(data, function(d){ return d.petal_width; });

// Coeff
			
			var xr = 0;
			var yr = 0;
			var term1 = 0;
			var term2 = 0;
			for (var i=0; i< data.length; i++){
				xr = parseFloat(data[i].petal_length) - x_mean;
				yr = parseFloat(data[i].petal_width) - y_mean;
				term1 += xr * yr;
				term2 += xr * xr;
				}

var b1 = term1 / term2;
			var b0 = y_mean - (b1 * x_mean);

for (i=0; i< data.length; i++){
				data[i].lin_reg_term = b0 + (data[i].petal_length * b1); 
				}

var line = d3.line()
				.x(function(d){ return x(d.petal_length); })
				.y(function(d){ return y(d.lin_reg_term); });

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

var clicked;
  
  var legend = svg.selectAll(".legend")
    .data(color.domain())
  .enter().append("g")
    .attr("class", "legend")
    .attr("transform", function(d, i) { return "translate(75," + i * 20+ ")"})
  .on("click", function(d){

d3.selectAll(".symbol").style("opacity", 1)
      if (clicked !==d){
        d3.selectAll(".symbol")
        	.filter(function (e){
          return e.species !==d
        })
        .style ("opacity", 0.1)
        clicked =d
     
      }
    else {clicked=null;}
    	
    
  });

legend.append("rect")
      .attr("x", 80)
      .attr("width", 18)
      .attr("height", 18)
  		.style("stroke", "#000")
      .style("fill", color);

legend.append("text")
      .attr("x", 75)
      .attr("y", 9)
      .attr("dy", ".35em")
      .style("text-anchor", "end")
      .text(function(d) { return d; });
  
  
  
  var rectangle = svg.append("rect")
      .attr("x", 70)
      .attr("y", 0)
  		.attr("width", 110)
  		.attr("height", 60)
 			.style("stroke", "#000")
      .style("fill", "none");

});

</script>

Modified http://d3js.org/d3.v4.min.js to a secure url

https://d3js.org/d3.v4.min.js