Function vRatio

libs/echarts/echarts.simple.js:15188–15190

(u, v)

    return Math.sqrt(v[0] * v[0] + v[1] * v[1]);
};
var vRatio = function (u, v) {
    return (u[0] * v[0] + u[1] * v[1]) / (vMag(u) * vMag(v));
};
var vAngle = function (u, v) {
    return (u[0] * v[1] < u[1] * v[0] ? -1 : 1)
            * Math.acos(vRatio(u, v));