An area chart filled by the sign of value

by patelsan

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.24/browser.js"></script>
<script src="https://npmcdn.com/[email protected]/dist/react-with-addons.min.js"></script>
<script src="https://npmcdn.com/[email protected]/dist/react-dom.min.js"></script>
<script src="https://npmcdn.com/prop-types/prop-types.min.js"></script>
<script src="https://npmcdn.com/recharts/umd/Recharts.min.js"></script>
<div id="container">
    <!-- This element's contents will be replaced with your component. -->
</div>

CSS

body {
  margin: 0;
}
#container {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  padding: 10px;
  width: 800px;
  height: 800px;
  background-color: #fff;
}

Babel + JSX

const {AreaChart, Area, XAxis, YAxis, CartesianGrid, Tooltip} = Recharts;

const data = [
  {name: 'Page A', uv: 4000, pv: 2400, amt: 2400},
  {name: 'Page B', uv: 3000, pv: 1398, amt: 2210},
  {name: 'Page C', uv: -1000, pv: 9800, amt: 2290},
  {name: 'Page D', uv: 500, pv: 3908, amt: 2000},
];


const gradientOffset = () => {
  const dataMax = Math.max(...data.map((i) => i.uv));
  const dataMin = Math.min(...data.map((i) => i.uv));

  if (dataMax <= 0){
  	return 0
  }
  else if (dataMin >= 0){
  	return 1
  }
  else{
  	return dataMax / (dataMax - dataMin);
  }
}

const off = gradientOffset();

const SimpleAreaChart = React.createClass({
	render () {
  	return (
    	<AreaChart
        width={600}
        height={400}
        data={data}
        margin={{top: 10, right: 30, left: 0, bottom: 0}}
      >
        <CartesianGrid strokeDasharray="3 3"/>
        <XAxis dataKey="name"/>
        <YAxis/>
        <Tooltip/>
        <defs>
          <linearGradient id="splitColor" x1="0" y1="0" x2="0" y2="1">
            <stop offset={off} stopColor="green" stopOpacity={1}/>
            <stop offset={off} stopColor="red" stopOpacity={1}/>
          </linearGradient>
        </defs>
        <Area type="monotone" dataKey="uv" stroke="#000" fill="url(#splitColor)" />
      </AreaChart>
    );
  }
})

ReactDOM.render(
  <SimpleAreaChart />,
  document.getElementById('container')
);