examples/barchart07_final.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>

    <div>
      <strong>Filter:</strong>
      <label><input type="checkbox" name="US" value="1" id="filter-us-only" />US only</label>
    </div>

    <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;

      // Scales setup
      const xscale = d3.scaleLinear().range([0, width]);
      const yscale = d3.scaleBand().rangeRound([0, height]).paddingInner(0.1);

      // Axis setup
      const xaxis = d3.axisTop().scale(xscale);
      const g_xaxis = g.append("g").attr("class", "x axis");
      const yaxis = d3.axisLeft().scale(yscale);
      const g_yaxis = g.append("g").attr("class", "y axis");

      /////////////////////////

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

        update(data);
      });

      function update(new_data) {
        //update the scales
        xscale.domain([0, d3.max(new_data, (d) => d.temperature)]);
        yscale.domain(new_data.map((d) => d.location.city));
        //render the axis
        g_xaxis.transition().call(xaxis);
        g_yaxis.transition().call(yaxis);

        // Render the chart with new data

        // DATA JOIN use the key argument for ensurign that the same DOM element is bound to the same data-item
        const rect = g
          .selectAll("rect")
          .data(new_data, (d) => d.location.city)
          .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
          .transition()
          .attr("height", yscale.bandwidth())
          .attr("width", (d) => xscale(d.temperature))
          .attr("y", (d) => yscale(d.location.city));

        rect.select("title").text((d) => d.location.city);
      }

      //interactivity
      d3.select("#filter-us-only").on("change", function () {
        // This will be triggered when the user selects or unselects the checkbox
        const checked = d3.select(this).property("checked");
        if (checked === true) {
          // Checkbox was just checked

          // Keep only data element whose country is US
          const filtered_data = data.filter((d) => d.location.country === "US");

          update(filtered_data); // Update the chart with the filtered data
        } else {
          // Checkbox was just unchecked
          update(data); // Update the chart with all the data we have
        }
      });
    </script>
  </body>
</html>