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htmlcsssvgd3.js

Position a DIV element inside an SVG viewport

How can I position a HTML DIV element relative to a SVG element?

I use D3 to generate a chart in SVG:

enter image description here

I would like to add a dropdown list on the bottom-right corner, next to the legend. I do have the corresponding element (a plain HTML DIV element,) but I do not know how to position it properly on the chart.

I understand positioning of SVG elements, but I do not know how to apply something similar to a DIV element.

Any idea, besides positioning it outside the viewport (e.g. below)?

Solution

  • Look into CSS Position. You can create a relatively positioned DIV to hold your SVG. You can then lay down an absolutely positioned DIV on top of it to hold the select element; you can place that second DIV anywhere you want using it's left and top styles.

    Here it is all put together:

    let w = 500;
let h = 300;
let pad = 10;
let xmin = -2 * Math.PI;
let xmax = 2 * Math.PI;
let ymin = -1.1;
let ymax = 1.1;

let svg = d3.select("#graph")
    .append("svg")
    .attr("max-width", `${w}px`)
    .attr("viewBox", [0, 0, w, h]);
    
let x_scale = d3
  .scaleLinear()
  .domain([xmin, xmax])
  .range([pad, w - pad]);
let y_scale = d3
  .scaleLinear()
  .domain([ymin, ymax])
  .range([h - pad, pad]);
let path = d3
  .line()
  .x((d) => x_scale(d[0]))
  .y((d) => y_scale(d[1]));

svg
  .append("g")
  .attr("transform", `translate(0, ${y_scale(0)})`)
  .call(d3.axisBottom(x_scale).tickFormat(d3.format("d")).tickSizeOuter(0));
svg
  .append("g")
  .attr("transform", `translate(${x_scale(0)})`)
  .call(d3.axisLeft(y_scale).ticks(5).tickSizeOuter(0));
  
d3.select('#function')
  .on('change', function() {
    draw_graph(this.value)
  })
  
  
draw_graph('sine')
  

function draw_graph(f_string) {
  svg.select('path.graph').remove()
  let f
  if(f_string == "sine") {
    f = Math.sin;
  }
  else {
    f = Math.cos;
  }
  let pts = d3.range(xmin, xmax, 0.01)
    .map((x) => [x, f(x)]);
  svg
    .append("path")
    .attr('class', 'graph')
    .attr("d", path(pts))
    .attr("fill", "none")
    .attr("stroke", "black")
    .attr("stroke-width", 3);
}
    <script src="https://d3js.org/d3.v7.min.js"></script>

<div style="position: relative" id="viz">
  <svg id="graph" width=500 height=300 style="border: solid 2px black"></svg>
  <div style="border: solid 0.5px black; background-color: rgba(255,255,255,0.7); position: absolute; left: 20px; top: 30px">
    <label for="function">function:</label>
    <select name="function" id="function">
      <option value="sine">sine</option>
      <option value="cosine">cosine</option>
    </select>
   </div>
</div>