An example of machine learning from https://youtu.be/wUPFOFbCeFI

Learn a line .js

let ys_and_xs = [ [1, 3.8], [2, 1.9], [3, 2.9], 
                  [4, 4.5], [5, 6.4], [6, 3.5], 
                  [7, 6.7], [8, 6.2], [9, 8.0] ];


function grade(a, b) {
    let error = 0;
    for ( [x,y] of ys_and_xs ) {
        error += Math.pow( a*x + b - y , 2 )
    }
    return error
}

function someChange() {
    return Math.random() - .5
}

let a = 1;
let b = 0;
let err = grade(a,b);

for( let i=0; i<100000; i++) {
    let new_a = a + someChange()
    let new_b = b + someChange()
    let new_err = grade(new_a, new_b)
    if ( new_err < err ) {
        a = new_a
        b = new_b
        err = new_err
        console.log("a =", a, ", b =", b)
    }
}