Filling a chart with a color above a specific Y value

I've been trying to fill a chart with color above certain Y value and I can't do it. What I tried to do is writing a condition that if the value is >3.5 that area of the chart will be filled with a different color.

splineSeries.fill(function() {
    if (this.value > 3.5)
    return '#d3f335 0.4'
    else
      return '#cdf0a7 0.6'})

However, this doesn't work for me as it fills the whole area of the chart which values are >3.5 and not only the area that it's above the line.

This is how that chunk of code is working in my chart.1

If you know how this can be solved I would really appreciate if you help me :)

Thanks!!

It does not seem AnyChart supports this kind of filling out of the box. You can however get creative with gradients:

  var cmin   = chart.getStat("yScalesMin");
  var cmax   = splineSeries.getStat('seriesMax');
  var cutoff = 3.5;
  
  splineSeries.fill({
    angle: 90,
    keys: [{
      color: '#cdf0a7',
      opacity: 0.6,
      offset: (cutoff-cmin) / (cmax-cmin)
    }, {
      color: '#d3f335',
      opacity: 0.4,
      offset: (cutoff-cmin) / (cmax-cmin)
    }],
    thickness: 3
  });

Here's a working example:

    chart = anychart.area();

    var series = chart.area(generateRandomData());

    var cmin   = chart.getStat("yScalesMin");
    var cmax   = series.getStat('seriesMax');
    var cutoff = 3.5;
  
    series.fill({
      angle: 90,
      keys: [{
        color: '#cdf0a7',
        opacity: 0.6,
        offset: (cutoff-cmin) / (cmax-cmin)
      }, {
        color: '#d3f335',
        opacity: 0.4,
        offset: (cutoff-cmin) / (cmax-cmin)
      }],
      thickness: 3
    });

    chart.container("chart");
    chart.draw();

    function generateRandomData() {
      var data = [];
      for (let i=0; i<16; i++) {
        data.push({x:i, value:Math.random() * 7.5});
      }
      return data;
    }

#chart {
  height: 400px;
}

    <script src="https://cdn.anychart.com/releases/8.11.0/js/anychart-core.min.js"></script>
    <script src="https://cdn.anychart.com/releases/8.11.0/js/anychart-cartesian.min.js"></script>
    <div id="chart"></div>

This should also work with charts with yScalesMin > 0