Line Chart

Usage

var LineChart = require( '@stdlib/plot/sparklines/unicode/line' );

LineChart( [data,] [options] )

Returns a chart instance.

var chart = new LineChart();

The constructor accepts the following options:

• autoRender: boolean indicating whether to re-render on a change event.
• bufferSize: data buffer size. If provided, data is kept in a first-in first-out (FIFO) buffer which cannot exceed the buffer size. Default: +infinity.
• data: chart data.
• description: chart description.
• infinities: boolean flag indicating whether to encode infinite values. Default: false.
• isDefined: accessor function indicating whether a datum is defined.
• label: data label.
• yMax: maximum value of the y-axis domain. If set to null, the maximum value is computed from the data.
• yMin: minimum value of the y-axis domain. If set to null, the minimum value is computed from the data.

Writable Properties

LineChart.prototype.autoRender

Rendering mode. If true, an instance renders on each 'change' event; otherwise, rendering must be triggered manually.

var chart = new LineChart();

// Set:
chart.autoRender = false;

// Get:
var mode = chart.autoRender;
// returns false

LineChart.prototype.bufferSize

Data buffer size. If set, this specifies the maximum number of data elements which can be rendered. Once the data buffer is full, each new datum results in the oldest datum being removed.

var chart = new LineChart();

// Set:
chart.bufferSize = 3;

// Get:
var size = chart.bufferSize;
// returns 3

chart.data = [ 1, 2, 3 ];

var data = chart.data;
// returns [ 1, 2, 3 ]

chart.push( 4 );

data = chart.data;
// returns [ 2, 3, 4 ]

Setting a data buffer size is useful when rendering data streams.

LineChart.prototype.data

Chart data. When set, the value must be either array-like or an ndarray and cannot exceed the bufferSize.

var Float64Array = require( '@stdlib/array/float64' );

var chart = new LineChart();

// Set:
chart.data = new Float64Array( [ 3.14, 5.0, -3.14, -1.0 ] );

// Get:
var data = chart.data;
// returns [ 3.14, 5.0, -3.14, -1.0 ]

Note that data is copied to an internal data buffer.

LineChart.prototype.description

Chart description.

var chart = new LineChart();

// Set:
chart.description = 'Daily stock prices for the past 30 days.';

// Get:
var desc = chart.description;
// returns 'Daily stock prices for the past 30 days.'

LineChart.prototype.infinities

Boolean flag indicating whether to render infinite values. When set to false, infinite values are considered missing values. When set to true, both positive and negative infinity are encoded as ∞.

var chart = new LineChart();

chart.infinities = true;

chart.data = [
    1.0,
    5.0,
    NaN,
    Infinity,
    4.0,
    -Infinity,
    3.0
];

var str = chart.render();
// returns '⡈⠉ ∞⢂∞⠒'

LineChart.prototype.isDefined( d, i )

An accessor function which defines whether a datum is defined. This accessor is used to define how missing values are encoded. When invoked, the function is provided two arguments:

• d: datum
• i: datum index

function isDefined( d ) {
    return ( d !== null );
}

var chart = new LineChart();

// Set:
chart.isDefined = isDefined;

// Get:
var fcn = chart.isDefined;
// returns <Function>

The default behavior is to ignore values which are NaN.

LineChart.prototype.label

Data label.

var chart = new LineChart();

// Set:
chart.label = 'beep';

// Get:
var label = chart.label;
// returns 'beep'

LineChart.prototype.yMin

Minimum value of the y-axis domain. If this value is set to a value other than null, the y-axis lower bound is fixed; otherwise, the minimum value is computed from the chart data.

var chart = new LineChart( [ -1.0, 5.0, -3.0, 2.0, -4.0, 4.0, 3.0 ] );

chart.yMin = 0.0;

var str = chart.render();
// returns '⡈⢁⡠⢄⡐⠒⠒'

LineChart.prototype.yMax

Maximum value of the y-axis domain. If this value is set to a value other than null, the y-axis upper bound is fixed; otherwise, the maximum value is computed based on the chart data.

var chart = new LineChart( [ -1.0, 5.0, -3.0, 2.0, -4.0, 4.0, 3.0 ] );

chart.yMax = 10.0;

var str = chart.render();
// returns '⠔⢂⡠⢄⡐⠒⠒'

Methods

LineChart.prototype.push( datum )

Appends data to a chart.

var chart = new LineChart( [ 1, 2, 3 ] );

var data = chart.data;
// returns [ 1, 2, 3 ]

chart.push( 4 );

data = chart.data;
// returns [ 1, 2, 3, 4 ]

LineChart.prototype.render()

Renders a line chart sparkline.

var chart = new LineChart( [ 1.0, 5.0, 3.0, 2.0, 4.0, 4.0, 3.0 ] );

var str = chart.render();
// returns '⡈⠑⠢⠔⠒⠒⠒'

LineChart.prototype.toString()

Serializes a line chart sparkline as a string by calling the render() method.

var chart = new LineChart( [ 1.0, 5.0, 3.0, 2.0, 4.0, 4.0, 3.0 ] );

var str = chart.toString();
// returns '⡈⠑⠢⠔⠒⠒⠒'

Events

'change'

Emitted whenever a property value changes.

var chart = new LineChart();

chart.on( 'change', onChange );

function onChange() {
    console.log( 'A property was updated.' );
}

'render'

Emitted whenever a sparkline is rendered.

var chart = new LineChart();

chart.on( 'render', onRender );

function onRender( str ) {
    console.log( 'Rendered sparkline: %s', str );
}