Iris Regression

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>D3 Page Template</title>
  			<script src="https://d3js.org/d3.v4.min.js"></script>
        <style>
          div.bar {
            display: inline-block;
            width: 20px;
            height: 75px;   /* We'll override height later */
            background-color: teal;
            margin-right: 2px;
          }
        </style>
    </head>

<body>
        <script type="text/javascript">
        //Définition des variables globales
        var w = 1000;
        var h = 500;
        var scalePadding = 80;
        var axisPadding = 60;
        var dataset;
        var xScale;
        var yScale;
        var xMax;
        var xMin;
        var yMax;
        var yMin;
        var xAxis;
        var yAxis;

//Chargement des données

d3.csv("iris.csv", function(error, data) {
          if (error) {
            console.log(error);
          } else {
            dataset = data;
            defineScales();
            drawScatterPlot();
            addAxes();
            draw_regression("setosa", "orange");
            draw_regression("versicolor", "red");
            draw_regression("virginica", "blue");
          }

xScale = d3.scaleLinear()
                        .domain([xMin, xMax])
                        .range([scalePadding, w - scalePadding])

yScale = d3.scaleLinear()
                        .domain([yMin, yMax])
                        .range([h - scalePadding, scalePadding])
        }

function drawScatterPlot(){
          // Axes
          xAxis = d3.axisBottom()
                        .scale(xScale);

yAxis = d3.axisLeft()
                        .scale(yScale);

// Scatterplot values
          var points = svg.selectAll(".point")
                      .data(dataset)
                      .enter()
                      .append("path")
                      .attr("fill", function(d){
                        if (d["species"] == "setosa") {return "orange"}
                        else if (d["species"] == "versicolor") {return "red"}
                        else if (d["species"] == "virginica") {return "blue"}
                      })
                      .attr("d", d3.symbol().type(function(d) {
                        if (d["species"] == "setosa") {return d3.symbolStar}
                        else if (d["species"] == "versicolor") {return d3.symbolCross}
                        else if (d["species"] == "virginica") {return d3.symbolCircle}
                      }))
                      .attr("transform", function(d) {return "translate(" + xScale(d["sepal_length"]) + "," + yScale(d["sepal_width"]) + ")";});

}

function draw_regression(species, color) {

// Filtered dataset with only selected species
          var ds = dataset.filter(function(d) {return d["species"] == species});

var x_mean = d3.mean(ds, function(d) {return d["sepal_length"]});
          var y_mean = d3.mean(ds, function(d) {return d["sepal_width"]});
          var term1 = 0;
          var term2 = 0;

for (i = 0; i < ds.length; i++) {
              xr = ds[i]["sepal_length"] - x_mean;
              yr = ds[i]["sepal_width"] - y_mean;
              term1 += xr * yr;
              term2 += xr * xr;
          }

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

// Plot the line for the regression
          console.log(xScale)
          var lines = svg.append("line")
                           .attr("x1", xScale(xMin))
                           .attr("y1", yScale(b0 + b1 * xMin))
                           .attr("x2", xScale(d3.max(dataset, function(d) {return d["sepal_length"]})))
                           .attr("y2", yScale(b0 + b1 * d3.max(dataset, function(d) {return d["sepal_length"]})))
                           .attr("stroke", color)
                           .attr("stroke-width", 2);
        }

function addAxes(){
          svg.append("g")
              .attr("transform", "translate(0," + (h - axisPadding) + ")")
              .call(xAxis);

svg.append("g")
              .attr("transform", "translate(" + axisPadding + ",0)")
              .call(yAxis);

svg.append("text")
              .attr("text-anchor", "middle")
              .attr("transform", "translate("+ (scalePadding/3) +","+(h/2)+")rotate(-90)")
              .attr("font-family", "sans-serif")
              .text("Sepal Width");

svg.append("text")
              .attr("text-anchor", "middle")
              .attr("transform", "translate("+ (w/2) +","+(h-(scalePadding/3))+")")
              .attr("font-family", "sans-serif")
              .text("Sepal Length");
        }

});

svg = d3.select("body")
                .append("svg")
                .attr("width", w)
                .attr("height", h);

</script>
    </body>
</html>

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