Bar chart transitions

// Specify the chart’s dimensions.
const height = 400;
const marginTop = 20;
const marginRight = 0;
const marginBottom = 30;
const marginLeft = 40;

// Declare the x (horizontal position) scale and the corresponding axis generator.
const x = d3.scaleBand()
    .domain(data.map((d) => d.letter))
    .range([marginLeft, width - marginRight])
    .padding(0.1);

// Declare the y (vertical position) scale.
const y = d3.scaleLinear()
    .domain([0, d3.max(data, (d) => d.frequency)]).nice()
    .range([height - marginBottom, marginTop]);

const xAxis = d3.axisBottom(x).tickSizeOuter(0);
const yAxis = d3.axisLeft(y).tickFormat((y) => (y * 100).toFixed());

// Create the SVG container.
const svg = d3.create("svg")
    .attr("width", width)
    .attr("height", height);

// Create a bar for each letter.
const bar = svg.append("g")
    .attr("fill", "steelblue")
  .selectAll("rect")
  .data(data)
  .join("rect")
    .style("mix-blend-mode", "multiply") // Darker color when bars overlap during the transition.
    .attr("x", (d) => x(d.letter))
    .attr("y", (d) => y(d.frequency))
    .attr("height", (d) => y(0) - y(d.frequency))
    .attr("width", x.bandwidth());

// Create the axes.
const gx = svg.append("g")
    .attr("transform", `translate(0,${height - marginBottom})`)
    .call(xAxis);

const gy = svg.append("g")
    .attr("transform", `translate(${marginLeft},0)`)
    .call(yAxis)
    .call((g) => g.select(".domain").remove());

display(svg.node());

// Given a comparator, transition the x-axis and bar positions accordingly.
function update(order) {
  x.domain(data.sort(order).map((d) => d.letter));

  const t = svg.transition()
      .duration(750);

  bar.data(data, (d) => d.letter)
      .order()
    .transition(t)
      .delay((d, i) => i * 20)
      .attr("x", (d) => x(d.letter));

  gx.transition(t)
      .call(xAxis)
    .selectAll(".tick")
      .delay((d, i) => i * 20);
}

update(order); // side effect to trigger transition

const data = FileAttachment("data/alphabet.csv").csv({typed: true}).then(display);