examples/barchart04_scale.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <title>Student's First Barchart</title>
    <meta name="description" content="Student's First Barchart" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js"></script>
    <script src="../web_modules/d3/dist/d3.js"></script>
    <link href="./style.css" rel="stylesheet" />
    <style>
      rect {
        fill: steelblue;
        fill-opacity: 0.8;
      }
      rect:hover {
        fill-opacity: 1;
      }
      .axis {
        font-size: smaller;
      }
    </style>
  </head>
  <body>
    <h1>Student's First Barchart</h1>

    <script>
      const margin = { top: 40, bottom: 10, left: 120, right: 20 };
      const width = 800 - margin.left - margin.right;
      const height = 600 - margin.top - margin.bottom;

      // Creates sources <svg> element
      const svg = d3
        .select("body")
        .append("svg")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom);

      // Group used to enforce margin
      const g = svg.append("g").attr("transform", `translate(${margin.left},${margin.top})`);

      // Global variable for all data
      let data;

      const bar_height = 50;

      /////////////////////////
      // TODO create an x and y scale and axis
      // x a linear scale with range: [0, width] and domain from 0 max temperature
      // y a band ordinal scale range: [0, height] and domain the different cities

      d3.json("weather.json").then((json) => {
        data = json;

        update(data);
      });

      function update(new_data) {
        // Render the chart with new data

        // DATA JOIN
        const rect = g
          .selectAll("rect")
          .data(new_data)
          .join(
            // ENTER
            // new elements
            (enter) => {
              const rect_enter = enter.append("rect").attr("x", 0);
              rect_enter.append("title");
              return rect_enter;
            },
            // UPDATE
            // update existing elements
            (update) => update,
            // EXIT
            // elements that aren't associated with data
            (exit) => exit.remove()
          );

        // ENTER + UPDATE
        // both old and new elements
        rect
          .attr("height", bar_height)
          .attr("width", (d) => d.temperature * 7)
          .attr("y", (d, i) => i * (bar_height + 5));

        rect.select("title").text((d) => d.location.city);
      }
    </script>
  </body>
</html>