Use + to coerce string values to int

apparently csv parser in d3 always assumes strings and need to do explicit coerce to get numbers for things like max with a + op.

HTML

<script src="http://d3js.org/d3.v3.min.js"></script>
<html>
    <body>

    </body>
</html>

JavaScript

var data = [ 
    {column1: 100, column3: 70,  column2: "a"},
    {column1: 9, column3: 50, column2: "b"},
    {column1: 2, column3: 90, column2: "c"},
];
    
    var o = { 
        maxWithCoerce: d3.max(data, function(d) { return [+d.column1 , d.column3]}),
        maxWithoutCoerce: d3.max(data, function(d) { return d.column1; })
    };

    d3.select("body").selectAll("div").data(d3.keys(o)).enter()
        .append("div")
        .text(function (d) {return d + "=" + o[d]});