Heat rules

Heat rules is a way to apply value-dependent setting values on series elements.

Prerequisites

In order for heat rules to function properly on series, it needs aggregate values (high and low) to be calculated for the series.

Normally, series does not do that in order not to waste resources.

To enable, we just need to set calculateAggregates setting to true:

let series = chart.series.push( 
  am5xy.ColumnSeries.new(root, { 
    name: "Series",
    xAxis: xAxis, 
    yAxis: yAxis, 
    valueYField: "value", 
    valueXField: "date",
    calculateAggregates: true
  })
);
var series = chart.series.push( 
  am5xy.ColumnSeries.new(root, { 
    name: "Series",
    xAxis: xAxis, 
    yAxis: yAxis, 
    valueYField: "value", 
    valueXField: "date",
    calculateAggregates: true
  })
);

Creating

A heat rule is a generic object that corresponds to IHeatRule interface.

It has the following required properties:

PropertyComment
targetA template for target element that heat rules will be applied to. E.g. column series' columns.template.
keyA settings key to apply heat value to on actual elements.
minLower end value of the spectrum, corresponding to the lowest value in all elements affected by the heat rule.
maxHigher end value of the spectrum, corresponding to the highest value in all elements affected by the heat rule.
dataFieldA data field to look for element's "value".

Series elements

To apply heat rules to series elements, like a column, we can use its template as a target for the heat rule.

Here's an example of a heat rule that applies color to column series columns based on their valueY data field (same data field that is used to determine column height).

series.set("heatRules", [{
  target: series.columns.template,
  dataField: "valueY",
  min: am5.color(0xff621f),
  max: am5.color(0x661F00),
  key: "fill"
}])
series.set("heatRules", [{
  target: series.columns.template,
  dataField: "valueY",
  min: am5.color(0xff621f),
  max: am5.color(0x661F00),
  key: "fill"
}])

See the Pen
Using templateField with ColumnSeries
by amCharts team (@amcharts)
on CodePen.0

Arbitrary value

We're not limited to binding to a data field that is used for actually plotting the series.

Each series also defines a generic "value" data field, which can be used for heat rules.

var series = chart.series.push( 
  am5xy.ColumnSeries.new(root, { 
    name: name,
    xAxis: xAxis, 
    yAxis: yAxis, 
    valueField: "heatValue",
    valueYField: field, 
    valueXField: "date",
    calculateAggregates: true
  }) 
);

series.setAll({
  heatRules: [{
    target: series.columns.template,
    dataField: "value",
    min: am5.color(0xff621f),
    max: am5.color(0x661F00),
    key: "fill"
  }]
});
var series = chart.series.push( 
  am5xy.ColumnSeries.new(root, { 
    name: name,
    xAxis: xAxis, 
    yAxis: yAxis, 
    valueField: "heatValue",
    valueYField: field, 
    valueXField: "date",
    calculateAggregates: true
  }) 
);

series.setAll({
  heatRules: [{
    target: series.columns.template,
    dataField: "value",
    min: am5.color(0xff621f),
    max: am5.color(0x661F00),
    key: "fill"
  }]
});

See the Pen
Heat rules on ColumnSeries
by amCharts team (@amcharts)
on CodePen.0

Bullets

Bullets do not have a dedicated template in series, so they need their template (for use in a heat rule) to be created explicitly:

let circleTemplate = am5.Template.new({});

series.bullets.push(function() {
  const bulletCircle = am5.Circle.new(root, {
    radius: 5,
    fill: series.get("fill"),
    fillOpacity: 0.8
  }, circleTemplate);
  
  return am5.Bullet.new(root, {
    sprite: bulletCircle
  });
});

// Add heat rules
series.set("heatRules", [{
  target: circleTemplate,
  min: 3,
  max: 60,
  dataField: "value",
  key: "radius"
}]);
var circleTemplate = am5.Template.new({});

series.bullets.push(function() {
  var bulletCircle = am5.Circle.new(root, {
    radius: 5,
    fill: series.get("fill"),
    fillOpacity: 0.8
  }, circleTemplate);
  
  return am5.Bullet.new(root, {
    sprite: bulletCircle
  });
});

// Add heat rules
series.set("heatRules", [{
  target: circleTemplate,
  min: 3,
  max: 60,
  dataField: "value",
  key: "radius"
}]);

The above creates a Template object, which is then passed in as a second parameter to new() method of a Circle class, so it is tied to a template.

We can then use that template in a heat rule to use on circle's radius setting.

See the Pen
XY scatter chart with heat rules on bullets
by amCharts team (@amcharts)
on CodePen.0

Custom value range

Heat rules will use aggregated high and low values from the data items of involved elements.

We can override that with absolutely custom values using heat rules minValue and maxValue settings.

series.set("heatRules", [{
  target: series.columns.template,
  dataField: "valueY",
  min: am5.color(0xff621f),
  max: am5.color(0x661F00),
  minValue: 0,
  maxValue: 1000,
  key: "fill"
}])
series.set("heatRules", [{
  target: series.columns.template,
  dataField: "valueY",
  min: am5.color(0xff621f),
  max: am5.color(0x661F00),
  minValue: 0,
  maxValue: 1000,
  key: "fill"
}])

NOTE If we set minValue and maxValue we don't need series to aggregate values, so the calculateAggregates does not need to be set.

Custom functions

If we need to do something fancier than just set value of a setting, we can use heat rule's customFunction property.

If set, instead of setting value of the setting directly on an element, this function will be called passing in the following parameters:

  • Target element (not a template, but an actual live element).
  • Min value
  • Max value
  • Value of the target element

It'll be up to the custom function to determine what settings and to what values to set.

series.set("heatRules", [{
  target: series.columns.template,
  dataField: "value",
  customFunction: function(sprite, min, max, value) {
    if (value < 100) {
      sprite.set("fill", am5.color(0xff0000));
    }
    else {
      sprite.set("fill", am5.color(0x00ff00));
    }
  }
}])
series.set("heatRules", [{
  target: series.columns.template,
  dataField: "value",
  customFunction: function(sprite, min, max, value) {
    if (value < 100) {
      sprite.set("fill", am5.color(0xff0000));
    }
    else {
      sprite.set("fill", am5.color(0x00ff00));
    }
  }
}])

Examples

Map chart

See the Pen
Map point series creating individual data items
by amCharts team (@amcharts)
on CodePen.0