Brushing for Force-Directed Graph

Basic brushing implementation for force-directed graph inspired in the following example.

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<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
    .links line {
        stroke: #999;
        stroke-opacity: 0.6;
    }
​
    .nodes circle {
        stroke: #fff;
        stroke-width: 1.5px;
    }
​
    .node .selected circle {
        fill: red;
    }
​
</style>
<svg width="960" height="600"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="force_brush.js"></script>
    

https://d3js.org/d3.v4.min.js