As a beginner in JavaScript, I am struggling to understand the following svg code snippet that uses JavaScript to define its x-coordinate and radius. While I grasp the concept of data binding, my confusion lies in determining where it is specified that the first argument 'd' represents the dataset and the second 'i' serves as a counter for the circles (0 for the first circle, 1 for the second, and so on).
var dataset = [ 5, 10, 15, 20, 25 ];
var circles = svg.selectAll("circle")
.data(dataset)
.enter()
.append("circle");
circles.attr("cx", function(d, i) {
return (i * 50) + 25;
})
.attr("cy", h/2)
.attr("r", function(d) {
return d;
});
Any insights would be greatly appreciated. Thank you.