如何在d3中获取plot坐标点？

Question

I have a JSON file with a number of coordinates, like so:

[
{
      "coord": [
          184.5247050,
          775.2556777
      ]
}, 
{
      "coord": [
          177.4747474,
          833.2566478
      ]
},
{
      "coord": [
          255.6434553,
          446.7733333
      ]
}
] 

I use this code with the d3 library, to try to plot the data on a canvas:

var svg = d3.select("#canvas");

d3.json(location_data, function(data){

svg.selectAll("circle")
                .data(data.coord)
                .enter()
                .append("circle")
                .attr("cx", function(element, index){
                return index;
                })
                .attr("cy", function(element, index){
                return index;
                })
                .attr("r", 30)
                .attr("fill", "lightgreen");
})

But I do not see any output. What is wrong with the code? How do I fix it?

Answer 1

The problem is that you bind the data using .data(data.coord) , but data is an array and has no coord attribute. You have to transform your object array to an array containing arrays of coordinates like so:

.data(data.map(d => d.coord))

You probably also need to change the way you set "cx" and "cy" attributes:

.attr("cx", d => d[0])
.attr("cy", d => d[1])