title: Importing data from .csv using d3.js
body: <p>I am trying to import some data from a .csv using d3.js.  I am having trouble doing this, and was wondering if anyone could lend a hand.  My .csv file is formatted like so:</p>
  
  <pre><code>max_i,min_i,max_f,min_f
  -122.1430195,-122.1430195,-122.415278,37.778643
  -122.1430195,-122.1430195,-122.40815,37.785034
  -122.4194155,-122.4194155,-122.4330827,37.7851673
  -122.4194155,-122.4194155,-122.4330827,37.7851673
  -118.4911912,-118.4911912,-118.3672828,33.9164666
  -121.8374777,-121.8374777,-121.8498415,39.7241178
  -115.172816,-115.172816,-115.078011,36.1586877
  -82.5618186,-82.5618186,-79.2274115,37.9308282
  -79.9958864,-79.9958864,-80.260396,40.1787544
  -74.1243063,-74.1243063,-74.040948,40.729688
  -106.609991,-106.609991,-106.015897,35.640949
  </code></pre>
  
  <p>I am trying to load the data using the following code:</p>
  
  <pre><code>var dataset = []
  d3.csv("data.csv", function(data) {
     dataset = data.map(function(d) { return [ +d["max_i"], +d["min_i"] ]; });
  });
  console.log(dataset)
  </code></pre>
  
  <p>However, I just get an empty [] in the console.  Can anyone point out my mistake?</p>