Pen Settings



CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

+ add another resource


Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource


Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.


Auto Save

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.


                <script src=""></script>

<input type="checkbox" id="repulsion-checkbbox" onclick="changeRepulsion(this.checked)"> Points repel

<svg id="scatterplot" width="400" height="300" style="background-color: #f0f0f0;"></svg>




                // Toy data with 5 points
let data = [
  {"x":50, "y":50, "r":10, "fill":"#990000", "fill_opacity": 0.4},
  {"x":55, "y":55, "r":20, "fill":"#009900", "fill_opacity": 0.4},
  {"x":60, "y":65, "r":15, "fill":"#000099", "fill_opacity": 0.4},
  {"x":130, "y":165, "r":10, "fill":"#009999", "fill_opacity": 0.4},
  {"x":130, "y":165, "r":20, "fill":"#900099", "fill_opacity": 0.4}

// Creates force simulation that, when enabled, allows points to repel each other
let sim = d3.forceSimulation(data);
sim.force("collision", d3.forceCollide(d => d.r)); // Repulsion force
sim.force("x_force", d3.forceX(d => d.x)); // Each point attacted to its center x and y
sim.force("y_force", d3.forceY(d => d.y));
sim.on('tick', drawPlot); // Redraws scatterplot at every simulation "tick"

// Uncomment both lines below lets simulation run forever with obvious movements
// sim.alphaDecay(0); // Allows simulation to run forever numerically
// sim.velocityDecay(0); // Movements become obvious

sim.stop(); // Simulation is off initially
drawPlot(); // Draws scatterplot (points overlap as simulation is off)

// Checks checkbox

 * Draws points and labels in scatterplot as described in data.
 * For points and labbels that are alreay draw, update their locations,
 * using (updated) values in data.
function drawPlot(){
  let points ="#scatterplot").selectAll("circle").data(data);
  let labels ="#scatterplot").selectAll("text").data(data);
  // For new points and labels (not drawn yet, e.g., when page loads), draw them
    .attr("cx", d => d.x)
    .attr("cy", d => d.y)
    .attr("r", d => d.r)
    .attr("fill", d => d.fill)
    .attr("fill-opacity", d => d.fill_opacity);
    .text(d => d.x + ", " + d.y)
    .attr("x", d => d.x + d.r)
    .attr("y", d => d.y)
    .attr("alignment-baseline", "middle"); // Vertically align text with point

  // For exiting points already drawn, update their locations, 
  // using (updated) values in data
    .attr("cx", d => d.x)
    .attr("cy", d => d.y);
    // .text(d => d.x + ", " + d.y)
    .attr("x", d => d.x + d.r)
    .attr("y", d => d.y);

* Points repel each other, when checkbbox is checked.
* When unchecked, repulson force is removed.
function changeRepulsion(isCheckboxChecked){
  if (isCheckboxChecked){
    sim.force("collision", d3.forceCollide(d => d.r)); // Add repulsion force back
  } else {
    sim.force("collision", null); // Removes repulsion force
  sim.alpha(1); // Alpha value of 1 resets simulation back to beginning