Up/Down Chart

Usage

var UpDownChart = require( '@stdlib/plot/sparklines/unicode/up-down' );

UpDownChart( [data,] [options] )

Returns a chart instance.

var chart = new UpDownChart();

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

Writable Properties

UpDownChart.prototype.autoRender

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

var chart = new UpDownChart();

// Set:
chart.autoRender = false;

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

UpDownChart.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 UpDownChart();

// 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.

UpDownChart.prototype.data

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

var Int8Array = require( '@stdlib/array/int8' );

var chart = new UpDownChart();

// Set:
chart.data = new Int8Array( [ -1, 1, 1, 1, 1, -1, -1, 1 ] );

// Get:
var data = chart.data;
// returns [ -1, 1, 1, 1, 1, -1, -1, 1 ]

Note that data is copied to an internal data buffer.

UpDownChart.prototype.description

Chart description.

var chart = new UpDownChart();

// Set:
chart.description = 'Wins and losses for the past 30 days.';

// Get:
var desc = chart.description;
// returns 'Wins and losses for the past 30 days.'

UpDownChart.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 ) {
    // Only consider "wins" as defined:
    return ( d === 1 );
}

var chart = new UpDownChart();

// Set:
chart.isDefined = isDefined;

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

The default behavior is to ignore any values which are not 1 or -1.

UpDownChart.prototype.label

Data label.

var chart = new UpDownChart();

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

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

Methods

UpDownChart.prototype.push( datum )

Appends data to a chart.

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

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

chart.push( 4 );

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

UpDownChart.prototype.render()

Renders an up/down chart sparkline.

var chart = new UpDownChart( [ -1, 1, 1, 1, 1, -1, -1, 1 ] );

var str = chart.render();
// returns '↓↑↑↑↑↓↓↑'

Glyphs:

If provided any other value other than 1 or -1, the value is encoded as a missing value.

UpDownChart.prototype.toString()

Serializes an up/down chart sparkline as a string by calling the render() method.

var chart = new UpDownChart( [ -1, 1, 1, 1, 1, -1, -1, 1 ] );

var str = chart.toString();
// returns '↓↑↑↑↑↓↓↑'

Events

'change'

Emitted whenever a property value changes.

var chart = new UpDownChart();

chart.on( 'change', onChange );

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

'render'

Emitted whenever a sparkline is rendered.

var chart = new UpDownChart();

chart.on( 'render', onRender );

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