Sparkline

Usage

var Sparkline = require( '@stdlib/plot/sparklines/base/ctor' );

Sparkline( [data,] [options] )

Returns a sparkline instance.

var sparkline = new Sparkline();
// returns <Sparkline>

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: sparkline data.
• description: sparkline description.
• isDefined: accessor function indicating whether a datum is defined.
• label: data label.

Writable Properties

Sparkline.prototype.autoRender

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

var sparkline = new Sparkline();

// Set:
sparkline.autoRender = false;

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

Sparkline.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 sparkline = new Sparkline();

// Set:
sparkline.bufferSize = 3;

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

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

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

sparkline.push( 4 );

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

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

Sparkline.prototype.data

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

var Float32Array = require( '@stdlib/array/float32' );

var sparkline = new Sparkline();

// Set:
sparkline.data = new Float32Array( [ 3.14, 5.0, -3.14, -1.0 ] );

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

Note that data is copied to an internal data buffer.

Sparkline.prototype.description

Sparkline description.

var sparkline = new Sparkline();

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

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

Sparkline.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 sparkline = new Sparkline();

// Set:
sparkline.isDefined = isDefined;

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

The default behavior is to ignore values which are NaN.

Sparkline.prototype.label

Data label.

var sparkline = new Sparkline();

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

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

Methods

Sparkline.prototype.push( datum )

Appends data to a sparkline.

var sparkline = new Sparkline();

// Set:
sparkline.data = [ 1, 2, 3 ];

// Get:
var data = sparkline.data;
// returns [ 1, 2, 3 ]

sparkline.push( 4 );

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

Sparkline.prototype._render()

Private method for rendering a sparkline. This method should be implemented by Sparkline descendants.

function render() {
    return '▁█▅▃▆▆▅';
}

var sparkline = new Sparkline();

sparkline._render = render;

Sparkline.prototype.render()

Public method for rendering a sparkline which internally invokes the private _render() method.

function render() {
    return '▁█▅▃▆▆▅';
}

var sparkline = new Sparkline();

sparkline._render = render;

var str = sparkline.render();
// returns '▁█▅▃▆▆▅'

Sparkline.prototype.toString()

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

function render() {
    return '▁█▅▃▆▆▅';
}

var sparkline = new Sparkline();

sparkline._render = render;

var str = sparkline.toString();
// returns '▁█▅▃▆▆▅'

Events

'change'

Emitted whenever a property value changes.

var sparkline = new Sparkline();

sparkline.on( 'change', onChange );

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

'render'

Emitted whenever a sparkline is rendered.

var sparkline = new Sparkline();

sparkline.on( 'render', onRender );

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