@nebula.js/sn-grid-chart

The grid chart uses symbols of varying size sorted in a grid to visualize a measure across two dimensions.
The measure is the metric that determines the size of the symbol in each crossing.

Requirements

Requires @nebula.js/stardust version 1.2.0 or later.

Installing

If you use npm: npm install @nebula.js/sn-grid-chart. You can also load through the script tag directly from https://unpkg.com.

Usage

``js
import { embed } from '@nebula.js/stardust';
import gridChart from '@nebula.js/sn-grid-chart';

// 'app' is an enigma app model
const nuked = embed(app, {
types: [
{
// register grid chart
name: 'sn-grid-chart',
load: () => Promise.resolve(gridChart),
},
],
});

// Rendering a simple grid chart
nuked.render({
element: document.querySelector('.grid'),
type: 'sn-grid-chart',
fields: ['Country', 'Year', '=Sum(Population)'],
properties: {
title: 'The historical populations of some European countries',
},
});
`

More examples

$3

The size and shape of the symbols can be modified.

`js
// Rendering a grid chart with customized symbols
nuked.render({
element: document.querySelector('.grid'),
type: 'sn-grid-chart',
// fields: ['Country', 'Year', '=Sum(Population)'],
properties: {
title: 'The historical populations of some European countries',
dataPoint: {
rangeBubbleSizes: [0.25, 0.85],
symbol: 'star',
},
},
});
`

$3

You can color the symbol by measure and add a legend to show more
information about the measure. The axis titles can be hidden
and the gridlines can be shown to further improve the look.

`js
// Rendering a customized grid chart
nuked.render({
element: document.querySelector('.grid'),
type: 'sn-grid-chart',

// Define all fields in properties
properties: {
title: 'The historical populations of some European countries',
qHyperCubeDef: {
qDimensions: [
{
qDef: { qFieldDefs: ['Country'] },
},
{
qDef: { qFieldDefs: ['Year'] },

qAttributeExpressions: [
{
qExpression: 'Sum(Population)',
id: 'colorByAlternative',
},
],
},
],
qMeasures: [
{
qDef: {
qDef: 'Sum(Population)',
},
},
],
qMode: 'T',
qAlwaysFullyExpanded: true,
},
color: {
auto: false,
mode: 'byMeasure',
measureScheme: 'dg',
reverseScheme: true,
},
legend: {
show: true,
dock: 'auto',
showTitle: true,
},
xAxis: {
show: 'label',
dock: 'near',
gridLines: true,
},
yAxis: {
show: 'label',
dock: 'near',
gridLines: true,
},
},
});
`

Grid chart plugins

A plugin can be passed into a grid chart to add or modify its capability
or visual appearance.
A plugin needs to be defined before it can be rendered together with the chart.

`js
// Step 1: define the plugin

// Modifying the look of the existing point component
const pointPlugin = {
info: {
name: 'point-plugin',
type: 'component-definition',
},
fn: ({ layout, keys }) => {
const componentDefinition = {
type: 'point',

// Provide the same name as the exisiting point component to override it
key: keys.COMPONENT.POINT,
settings: {
strokeWidth: '2px',
stroke: 'dimgray',

// Using data property 'd' and layout as input for helper functions
size: (d) => getSizeInLogarithmScale(d, layout),
fill: (d) => getColorBasedOnMedian(d),
},
};
return componentDefinition;
},
};

// Step 2: passing the plugin definition into the render function

// Rendering a grid chart with plugins
nuked.render({
element: document.getElementById('object'),
type: 'sn-grid-chart',
fields: ['Country', 'Year', '=Sum(Population)'],
plugins: [pointPlugin],
properties: {
title: 'The historical population of some European countries',
xAxis: { show: 'labels', gridLines: true },
yAxis: { show: 'labels', gridLines: true },
},
});
`

The plugin definition is an object, with two properties info and fn.
The fn returns a picasso.js component. To build this component,
some important chart internals are passed into the argument object of fn.

`js
// Structure of the argument object of fn
const pluginArgs = {
layout,
keys: {
SCALE: {
X,
Y,
},
COMPONENT: {
X_AXIS,
Y_AXIS,
POINT,
},
COLLECTION: {
MAIN,
},
},
};
`

With plugins, you can either add new components or modify existing components
of the grid chart.

$3

The new component can be a standard Picasso component
or a custom Picasso component. Here we demo a custom component
which add labels next to the grid bubbles.

`js
// Implementing a custom labels plugin, so that we can use it later
const labelsPluginDefinition = {
info: {
componentName: 'custom-labels-plugin',
name: 'custom-labels-plugin',
type: 'custom-component',
},
fn: () => {
const implementation = {
require: ['chart', 'renderer'],
render() {
const { items } = this.chart.component('point-component').data;
const scale = this.chart.scales();
const { width, height } = this.rect;
const labels = items.map((item) => ({
type: 'text',
text: item.size.label,
x: (scale.x(item.x.value) + scale.x.bandwidth() 0.5) width,
y: (scale.y(item.y.value) + scale.y.bandwidth() 0.2) height,
anchor: 'middle',
fill: 'dimgray',
}));
return labels;
},
};
return implementation;
},
};

// Using the labels plugin, defined above
const labelsPlugin = {
info: {
name: 'labels',
type: 'component-definition',
},
fn: ({ keys }) => {
const componentDefinition = {
// The type has to match with the componentName of the labels plugin definition above
type: 'custom-labels-plugin',
key: 'my-labels',
};
return componentDefinition;
},
};
`

$3

As an example, the positions and the appearance of the axes can be
modified completely by plugins.

To overide an existing component, fn should returns a picasso.js component
that has the same key as the existing component (keys.COMPONENT.X_AXIS in
this example)

`js
// Modifying the look and the position of the x-axis
const xAxisPlugin = {
info: {
name: 'x-axis-plugin',
type: 'component-definition',
},
fn: ({ keys, layout }) => {
const componentDefinition = {
type: 'axis',

// Provide the same name as the exisiting x-axis component to override it
key: keys.COMPONENT.X_AXIS,
layout: { dock: 'top' },
settings: {
labels: {
fontFamily: 'Cambria, serif',
fontSize: '15px',
fill: 'dimgray',
},
line: { stroke: 'gray' },
},
};
return componentDefinition;
},
};

// y-axis plugin can be defined with similar code
// ...
``

$3

- The plugins API is still experimental.
- We can not guarantee our charts to be compatible with all different settings, especially when modifying existing components.