Line Chart

A line chart is a way of plotting data points on a line. Often, it is used to show trend data, or the comparison of two data sets.

const config = { type: 'line', data: data, };

const config = {
  type: 'line',
  data: data,
};

const labels = Utils.months({count: 7}); const data = { labels: labels, datasets: [{ label: 'My First Dataset', data: [65, 59, 80, 81, 56, 55, 40], fill: false, borderColor: 'rgb(75, 192, 192)', tension: 0.1 }] };

const labels = Utils.months({count: 7});
const data = {
  labels: labels,
  datasets: [{
    label: 'My First Dataset',
    data: [65, 59, 80, 81, 56, 55, 40],
    fill: false,
    borderColor: 'rgb(75, 192, 192)',
    tension: 0.1
  }]
};

Dataset Properties

Namespaces:

• data.datasets[index] - options for this dataset only
• options.datasets.line - options for all line datasets
• options.elements.line - options for all line elements
• options.elements.point - options for all point elements
• options - options for the whole chart

The line chart allows a number of properties to be specified for each dataset. These are used to set display properties for a specific dataset. For example, the colour of a line is generally set this way.

Name	Type	Scriptable	Indexable	Default
backgroundColor	Color	Yes	-	'rgba(0, 0, 0, 0.1)'
borderCapStyle	string	Yes	-	'butt'
borderColor	Color	Yes	-	'rgba(0, 0, 0, 0.1)'
borderDash	number[]	Yes	-	[]
borderDashOffset	number	Yes	-	0.0
borderJoinStyle	'round'|'bevel'|'miter'	Yes	-	'miter'
borderWidth	number	Yes	-	3
clip	number|object|false	-	-	undefined
cubicInterpolationMode	string	Yes	-	'default'
data	object|object[]| number[]|string[]	-	-	required
drawActiveElementsOnTop	boolean	Yes	Yes	true
fill	boolean|string	Yes	-	false
hoverBackgroundColor	Color	Yes	-	undefined
hoverBorderCapStyle	string	Yes	-	undefined
hoverBorderColor	Color	Yes	-	undefined
hoverBorderDash	number[]	Yes	-	undefined
hoverBorderDashOffset	number	Yes	-	undefined
hoverBorderJoinStyle	'round'|'bevel'|'miter'	Yes	-	undefined
hoverBorderWidth	number	Yes	-	undefined
indexAxis	string	-	-	'x'
label	string	-	-	''
order	number	-	-	0
pointBackgroundColor	Color	Yes	Yes	'rgba(0, 0, 0, 0.1)'
pointBorderColor	Color	Yes	Yes	'rgba(0, 0, 0, 0.1)'
pointBorderWidth	number	Yes	Yes	1
pointHitRadius	number	Yes	Yes	1
pointHoverBackgroundColor	Color	Yes	Yes	undefined
pointHoverBorderColor	Color	Yes	Yes	undefined
pointHoverBorderWidth	number	Yes	Yes	1
pointHoverRadius	number	Yes	Yes	4
pointRadius	number	Yes	Yes	3
pointRotation	number	Yes	Yes	0
pointStyle	pointStyle	Yes	Yes	'circle'
segment	object	-	-	undefined
showLine	boolean	-	-	true
spanGaps	boolean|number	-	-	undefined
stack	string	-	-	'line'
stepped	boolean|string	-	-	false
tension	number	-	-	0
xAxisID	string	-	-	first x axis
yAxisID	string	-	-	first y axis

All these values, if undefined, fallback to the scopes described in option resolution

General

Name	Description
clip	How to clip relative to chartArea. Positive value allows overflow, negative value clips that many pixels inside chartArea. 0 = clip at chartArea. Clipping can also be configured per side: clip: {left: 5, top: false, right: -2, bottom: 0}
drawActiveElementsOnTop	Draw the active points of a dataset over the other points of the dataset
indexAxis	The base axis of the dataset. 'x' for horizontal lines and 'y' for vertical lines.
label	The label for the dataset which appears in the legend and tooltips.
order	The drawing order of dataset. Also affects order for stacking, tooltip and legend. more
stack	The ID of the group to which this dataset belongs to (when stacked, each group will be a separate stack). more
xAxisID	The ID of the x-axis to plot this dataset on.
yAxisID	The ID of the y-axis to plot this dataset on.

Point Styling

The style of each point can be controlled with the following properties:

Name	Description
pointBackgroundColor	The fill color for points.
pointBorderColor	The border color for points.
pointBorderWidth	The width of the point border in pixels.
pointHitRadius	The pixel size of the non-displayed point that reacts to mouse events.
pointRadius	The radius of the point shape. If set to 0, the point is not rendered.
pointRotation	The rotation of the point in degrees.
pointStyle	Style of the point. more...

All these values, if undefined, fallback first to the dataset options then to the associated elements.point.* options.

Line Styling

The style of the line can be controlled with the following properties:

Name	Description
backgroundColor	The line fill color.
borderCapStyle	Cap style of the line. See MDN (opens new window).
borderColor	The line color.
borderDash	Length and spacing of dashes. See MDN (opens new window).
borderDashOffset	Offset for line dashes. See MDN (opens new window).
borderJoinStyle	Line joint style. See MDN (opens new window).
borderWidth	The line width (in pixels).
fill	How to fill the area under the line. See area charts.
tension	Bezier curve tension of the line. Set to 0 to draw straightlines. This option is ignored if monotone cubic interpolation is used.
showLine	If false, the line is not drawn for this dataset.
spanGaps	If true, lines will be drawn between points with no or null data. If false, points with null data will create a break in the line. Can also be a number specifying the maximum gap length to span. The unit of the value depends on the scale used.

If the value is undefined, the values fallback to the associated elements.line.* options.

Interactions

The interaction with each point can be controlled with the following properties:

Name	Description
pointHoverBackgroundColor	Point background color when hovered.
pointHoverBorderColor	Point border color when hovered.
pointHoverBorderWidth	Border width of point when hovered.
pointHoverRadius	The radius of the point when hovered.

cubicInterpolationMode

The following interpolation modes are supported.

• 'default'
• 'monotone'

The 'default' algorithm uses a custom weighted cubic interpolation, which produces pleasant curves for all types of datasets.

The 'monotone' algorithm is more suited to y = f(x) datasets: it preserves monotonicity (or piecewise monotonicity) of the dataset being interpolated, and ensures local extremums (if any) stay at input data points.

If left untouched (undefined), the global options.elements.line.cubicInterpolationMode property is used.

Segment

Line segment styles can be overridden by scriptable options in the segment object. Currently all of the border* and backgroundColor options are supported. The segment styles are resolved for each section of the line between each point. undefined fallbacks to main line styles.

TIP

To be able to style gaps, you need the spanGaps option enabled.

Context for the scriptable segment contains the following properties:

• type: 'segment'
• p0: first point element
• p1: second point element
• p0DataIndex: index of first point in the data array
• p1DataIndex: index of second point in the data array
• datasetIndex: dataset index

Example usage

Stepped

The following values are supported for stepped.

• false: No Step Interpolation (default)
• true: Step-before Interpolation (eq. 'before')
• 'before': Step-before Interpolation
• 'after': Step-after Interpolation
• 'middle': Step-middle Interpolation

If the stepped value is set to anything other than false, tension will be ignored.

Default Options

It is common to want to apply a configuration setting to all created line charts. The global line chart settings are stored in Chart.overrides.line. Changing the global options only affects charts created after the change. Existing charts are not changed.

For example, to configure all line charts with spanGaps = true you would do:

Chart.overrides.line.spanGaps = true;

Data Structure

All of the supported data structures can be used with line charts.

Stacked Area Chart

Line charts can be configured into stacked area charts by changing the settings on the y-axis to enable stacking. Stacked area charts can be used to show how one data trend is made up of a number of smaller pieces.

const stackedLine = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            y: {
                stacked: true
            }
        }
    }
});

Vertical Line Chart

A vertical line chart is a variation on the horizontal line chart. To achieve this you will have to set the indexAxis property in the options object to 'y'. The default for this property is 'x' and thus will show horizontal lines.

const config = { type: 'line', data: data, options: { indexAxis: 'y', scales: { x: { beginAtZero: true } } } };

const config = {
  type: 'line',
  data: data,
  options: {
    indexAxis: 'y',
    scales: {
      x: {
        beginAtZero: true
      }
    }
  }
};

const labels = Utils.months({count: 7}); const data = { labels: labels, datasets: [{ axis: 'y', label: 'My First Dataset', data: [65, 59, 80, 81, 56, 55, 40], fill: false, backgroundColor: [ 'rgba(255, 99, 132, 0.2)', 'rgba(255, 159, 64, 0.2)', 'rgba(255, 205, 86, 0.2)', 'rgba(75, 192, 192, 0.2)', 'rgba(54, 162, 235, 0.2)', 'rgba(153, 102, 255, 0.2)', 'rgba(201, 203, 207, 0.2)' ], borderColor: [ 'rgb(255, 99, 132)', 'rgb(255, 159, 64)', 'rgb(255, 205, 86)', 'rgb(75, 192, 192)', 'rgb(54, 162, 235)', 'rgb(153, 102, 255)', 'rgb(201, 203, 207)' ], borderWidth: 1 }] };

const labels = Utils.months({count: 7});
const data = {
  labels: labels,
  datasets: [{
    axis: 'y',
    label: 'My First Dataset',
    data: [65, 59, 80, 81, 56, 55, 40],
    fill: false,
    backgroundColor: [
      'rgba(255, 99, 132, 0.2)',
      'rgba(255, 159, 64, 0.2)',
      'rgba(255, 205, 86, 0.2)',
      'rgba(75, 192, 192, 0.2)',
      'rgba(54, 162, 235, 0.2)',
      'rgba(153, 102, 255, 0.2)',
      'rgba(201, 203, 207, 0.2)'
    ],
    borderColor: [
      'rgb(255, 99, 132)',
      'rgb(255, 159, 64)',
      'rgb(255, 205, 86)',
      'rgb(75, 192, 192)',
      'rgb(54, 162, 235)',
      'rgb(153, 102, 255)',
      'rgb(201, 203, 207)'
    ],
    borderWidth: 1
  }]
};

Config Options

The configuration options for the vertical line chart are the same as for the line chart. However, any options specified on the x-axis in a line chart, are applied to the y-axis in a vertical line chart.

Internal data format

{x, y}