TP2

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
      // Margin setup
      var margin = {top: 20, right: 20, bottom: 20, left: 40},
          width = 960 - margin.left - margin.right,
          height = 500 - margin.top - margin.bottom;

// Basic SVG canvas
      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 + ")");

//mappings
      var symb={'setosa':d3.symbolCross,'versicolor':d3.symbolStar,'virginica':d3.symbolWye}
      var col={'setosa':'red','versicolor':'yellow','virginica':'orange'}

//data
     d3.csv('iris.csv', function(error,data){

data.forEach(function(d) {
                      d.sepal_length = +d.sepal_length;
                      d.sepal_width = +d.sepal_width;});

//scales
      var x = d3.scaleLinear()
          .range([0,width])
          .domain(d3.extent(data, function(d) { return d.sepal_length; }));

var y = d3.scaleLinear()
          .range([height,0])
          .domain([0, d3.max(data, function(d) { return d.sepal_width; })]);

//axis
      var xAxis = d3.axisBottom(x)

var yAxis = d3.axisLeft(y)

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

svg.append("g")
          .attr("class", "y axis")
          .call(yAxis)
          .append("text")

//line

var trend=trend_line(data);

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

svg.append("path")
          .datum(trend)
          .attr("class", "line")
          .attr("d", line)
          .style("stroke-width",2)
          .style('stroke','green');

var paths=svg.selectAll('path').data(data)
                        .enter()
                        .append('path')
                        .attr('class','symbol')
                        .attr("d", d3.symbol().type(function(d){return symb[d.species] }))
                        .attr("transform", function(d) { return "translate(" + 					    x(d.sepal_length) + ",+" + y(d.sepal_width) + ")";})
                        .style('fill',function(d) {return col[d.species]});

})

function trend_line(data) {

var x = [];
         var y = [];
        data.map(function(d) {
            x.push(d.sepal_length);
            y.push(d.sepal_width);
          });
          var n = x.length;
          var x_mean = 0;
          var y_mean = 0;
          var term1 = 0;
          var term2 = 0;
          // compute means
          for (var i = 0; i < n; i++) {
              x_mean += x[i]
              y_mean += y[i]
          }
          // calculate mean x and y
          x_mean /= n;
          y_mean /= n;

// calculate coefficients
          var xr = 0;
          var yr = 0;
          for (i = 0; i < x.length; i++) {
              xr = x[i] - x_mean;
              yr = y[i] - y_mean;
              term1 += xr * yr;
              term2 += xr * xr;

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

yhat = [];
          // fit line using coeffs
          for (i = 0; i < x.length; i++) {
              yhat.push(b0 + (x[i] * b1));
          }

var data = [];
          for (i = 0; i < y.length; i++) {
              data.push(
              {"yhat": yhat[i],
               "x": x[i]
              })
          }
          return (data);
      };

</script>
</body>

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