A", value: 4},
   {group: "B", value: 16},
   {group: "C", value: 8}
];

const data2 = [
   {group: "A", value: 7},
   {group: "B", value: 1},
   {group: "C", value: 20},
   {group: "D", value: 10}
];

// set the dimensions and margins of the graph
const margin = {top: 30, right: 30, bottom: 70, left: 60},
    width = 460 - margin.left - margin.right,
    height = 400 - margin.top - margin.bottom;

// append the svg object to the body of the page
const svg = d3.select("#my_dataviz")
  .append("svg")
    .at