D3 Examples - 14 - Colour gradient for an area fill

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<!DOCTYPE html>
<meta charset="utf-8">
<style> /* set the CSS */
​
body { font: 12px Arial;}
​
path {
    stroke: LightGray;
    stroke-width: 2;
    fill: none;
}
​
.axis path,
.axis line {
    fill: none;
    stroke: Silver;
    stroke-width: 1;
    shape-rendering: crispEdges;
}
​
  .area{
    fill: url(#area-gradient);
    stroke-width: 2px;
  }
  
</style>
<body>
​
<!-- load the d3.js library -->
<script src="https://d3js.org/d3.v3.min.js"></script>
​
<script>
​
    // Set the dimensions of the canvas / graph
    var margin = {top: 30, right: 20, bottom: 30, left: 50},
            width = 600 - margin.left - margin.right,
            height = 270 - margin.top - margin.bottom;
​
    // Parse the date / time
    var parseDate = d3.time.format("%d-%b-%y").parse;
    var formatTime = d3.time.format("%e %B");
​
    // Set the ranges
    var x = d3.time.scale().range([0, width]);
    var y = d3.scale.linear().range([height, 0]);
​
    // Define the axes
    var xAxis = d3.svg.axis().scale(x)
            .orient("bottom").ticks(5);
​
    var yAxis = d3.svg.axis().scale(y)
            .orient("left").ticks(5);
​
    // Define the line
    var area = d3.svg.area()
            .x(function(d) { return x(d.date); })
                    .y0(height)
            .y1(function(d) { return y(d.close); });
​
    var div = d3.select("body").append("div")
            .attr("class", "tooltip")
            .style("opacity", 0);
​
    // Adds the svg canvas
    var svg = d3.select("body")
            .append("svg")
            .attr("width", width + margin.left + margin.right)
            .attr("height", height + margin.top + margin.bottom)
            .append("g")
            .attr("transform",
                    "translate(" + margin.left + "," + margin.top + ")");
​
    // Get the data
    d3.csv("data.csv", function(error, data) {
        data.forEach(function(d) {
            d.date = parseDate(d.date);
            d.close = +d.close;
        });
​
        // Scale the range of the data
        x.domain(d3.extent(data, function(d) { return d.date; }));
        y.domain([0, d3.max(data, function(d) { return d.close; })]);
​
      svg.append("linearGradient")
        .attr("id", "area-gradient")
        .attr("gradientUnits", "userSpaceOnUse")
        .attr("x1", 0).attr("y1", y(0))
        .attr("x2", 0).attr("y2", y(1000))
      .selectAll("stop")
        .data([
        {offset: "0%", color: "red"},
        {offset: "30%", color: "red"},
        {offset: "45%", color: "black"},
        {offset: "55%", color: "black"},
        {offset: "60%", color: "lawngreen"},
        {offset: "100%", color: "lawngreen"}
      ])
      .enter().append("stop")
        .attr("offset", function(d) { return d.offset; })
        .attr("stop-color", function(d) {return d.color;});
  
      
      // Add the valueline path.
        svg.append("path")
                        .datum(data)
                .attr("class", "area")
                .attr("d", area);
      
     
        // Add the X Axis
        svg.append("g")
                .attr("class", "x axis")
                .attr("transform", "translate(0," + height + ")")
                .call(xAxis);
​
        // Add the Y Axis
        svg.append("g")
                .attr("class", "y axis")
                .call(yAxis);
​
    });
​
</script>
</body>
    