D3.js linear regression

Question

I searched for some help on building linear regression and found some examples here:
nonlinear regression function
and also some js libraries that should cover this

Answer 1

I made it work using the following code found here:

   function linearRegression(y,x){

        var lr = {};
        var n = y.length;
        var sum_x = 0;
        var sum_y = 0;
        var sum_xy = 0;
        var sum_xx = 0;
        var sum_yy = 0;

        for (var i = 0; i < y.length; i++) {

            sum_x += x[i];
            sum_y += y[i];
            sum_xy += (x[i]*y[i]);
            sum_xx += (x[i]*x[i]);
            sum_yy += (y[i]*y[i]);
        } 

        lr['slope'] = (n * sum_xy - sum_x * sum_y) / (n*sum_xx - sum_x * sum_x);
        lr['intercept'] = (sum_y - lr.slope * sum_x)/n;
        lr['r2'] = Math.pow((n*sum_xy - sum_x*sum_y)/Math.sqrt((n*sum_xx-sum_x*sum_x)*(n*sum_yy-sum_y*sum_y)),2);

        return lr;

};

var yval = dataset.map(function (d) { return parseFloat(d.xHeight); });
var xval = dataset.map(function (d) { return parseFloat(d.Ascendenti); });


var lr = linearRegression(yval,xval);
// now you have:
// lr.slope
// lr.intercept
// lr.r2
console.log(lr);

And then plotting a line with:

var max = d3.max(dataset, function (d) { return d.OvershootingSuperiore; });
var myLine = svg.append("svg:line")
            .attr("x1", x(0))
            .attr("y1", y(lr.intercept))
            .attr("x2", x(max))
            .attr("y2", y( (max * lr.slope) + lr.intercept ))
            .style("stroke", "black");

Using the code I found here