/* --- MY CODE START --- */
var intervalID = setInterval(animationTick, 1000);

function animationTick() {

    var randomInt = Number(getRandomInt(0, 5));
    var currentRadius = Number(node.attr("r"));
    var newRadius = Number(currentRadius + randomInt);

    node.attr("r", function (d) {return currentRadius + randomInt;});
}
/* --- MY CODE END --- */