title: Error: Invalid value for <rect> attribute width="NaN"
body: <p>I'm completely new to d3.  Ive have completed quite a few charts and examples from "Interactive Data Visualization for the Web" by Scott Murray and had very few problems. This is my first attempt at using a large data-set that is not contained within my code.</p>
  
  <p>d3.csv("historical_weather.csv", function(error,data) {</p>
  
  <pre><code>    dataset = data.map(function(d){ 
          return [ parseInt(+d.cloudCover),parseInt(+ d.maxTemp) ];
      })
  
      console.log(dataset); 
  
      var svg = d3.select("body")
          .append("svg")
          .attr("height",500)
          .attr("width",500);
  
      d3.select("svg")
          .selectAll("rect")
          .data("dataset")
          .enter()
          .append("rect")
          .attr("height",50)
          .attr("width", function(d){return d.maxTemp*10;});
  
  });
  </code></pre>
  
  <p>The data loads and is visible in the console as an array, I can see the expected values when digging into the array. However the console shows :</p>
  
  <blockquote>
    <p>Error: Invalid value for  attribute width="NaN"</p>
  </blockquote>