npm package: @nebula.js/sn-combo-chart
Description: Combo chart supernova
Author: QlikTech International AB
Latest version: 1.38.0

# @nebula.js/sn-combo-chart

The combo chart is suitable for comparing two sets of measure values that have
different scale. In its simplest form, a combo chart has one dimension and
two measures and is basically a bar chart combined with a line chart.

## Requirements

Requires `@nebula.js/stardust` version `1.7.0` or later.

## Installing

If you use npm: `npm install @nebula.js/sn-combo-chart`. You can also load through the script tag directly from [https://unpkg.com](https://unpkg.com/@nebula.js/sn-combo-chart).

## Usage

In the example below, the Bitcoin price and trade volume in the Bitfinex
platform are plotted in a combo chart. Despite being two different measures,
they show apparent correlation.

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

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

// Rendering a simple combo chart
nuked.render({
  element: document.querySelector('.combo'),
  type: 'combo-chart',
  fields: ['Date.autoCalendar.YearMonth', '=Avg(Price_Bitfinex)', '=Avg(Volume_Bitfinex)'],
  properties: {
    title: 'Bitcoin Price and Trading Volume (USD)',
  },
});
```

## More examples

### Customize the look of bars and lines

You can make the previous chart more appealing by making the bars thicker.
For the line, you can change its color, add data points and curviness.

```js
nuked.render({
  element: document.querySelector('.combo'),
  type: 'combo-chart',
  fields: ['Date.autoCalendar.YearMonth', '=Avg(Price_Bitfinex)', '=Avg(Volume_Bitfinex)'],

  // Customizing bars and lines
  properties: {
    title: 'Bitcoin Price and Trading Volume (USD)',
    components: [
      {
        key: 'bar',
        style: {
          strokeWidth: 'large',
          strokeColor: {
            color: '#25A0A8',
          },
        },
      },
      {
        key: 'line',
        style: {
          lineThickness: 3,
          lineCurve: 'monotone',
        },
      },
    ],
    dataPoint: {
      show: true,
    },
    color: {
      auto: false,
      mode: 'primary',
      paletteColor: {
        color: '#be3b03',
      },
    },
  },
});
```

### Use markers instead of bars

Beside bars and lines, there is a third option: markers. In the following
example, the bars from the previous chart are replaced by markers.

To override the default mesure configuration (one bar series, one line), the
measures are defined in `properties` instead of in `fields`.

```js
nuked.render({
  element: document.querySelector('.combo'),
  type: 'combo-chart',
  fields: ['Date.autoCalendar.YearMonth'],

  // Define measures in `properties`, instead of in `fields`
  properties: {
    title: 'Bitcoin Price and Trading Volume (USD)',
    qHyperCubeDef: {
      qMeasures: [
        {
          qDef: {
            qDef: '=Avg(Price_Bitfinex)',
            series: { axis: 0, type: 'marker', marker: 'triangle' },
          },
        },
        {
          qDef: {
            qDef: '=Avg(Volume_Bitfinex)',
            series: { axis: 1, type: 'line' },
          },
        },
      ],
    },
  },
});
```

### Horizontal combo chart

By default, the combo chart is oriented vertically like in
the previous examples: the bars are vertical and the line is horizontal.
If you wish, you can change the chart orientation to horizontal.

```js
nuked.render({
  element: document.querySelector('.combo'),
  type: 'combo-chart',
  fields: ['Date.autoCalendar.YearMonth', '=Avg(Price_Bitfinex)', '=Avg(Volume_Bitfinex)'],

  // Making the combo chart horizontal
  properties: {
    title: 'Bitcoin Price and Trading Volume (USD)',

    // You should set this ...
    orientation: 'horizontal',

    // ... but alse these to turn off continuous dimension scale
    dimensionAxis: {
      continuousAuto: false,
    },
    preferContinuousAxis: false,

    // Just make the line looks better
    components: [
      {
        key: 'line',
        style: {
          lineThickness: 3,
          lineCurve: 'monotone',
        },
      },
    ],
  },
});
```

### Comparing two pairs of measures

You can add multiple measures into a combo chart. Each measure can
be either a series of bar, a line, or a series of markers.

In the following example, by using two series of bars and two lines,
the Bitcoin price and trading volume of two different trading platforms
can be compared in the same chart.

Some notes about the code:

- By default, if you add 4 measures, you get one bar series and
  three lines. To define two bar series and two lines instead, you have
  to specify that in `properties` in stead of in `fields`.
- To customize colors of bars and lines, the `BASIC_COLOR_OPTIONS_PER_MEASURE`
  flag has to be on. Customized colors are defined in `qDef`.
- The `preferContinuousAxis` should be set to `false` (turn off continuous
  dimension scale) for the bars to be grouped instead of stacked.

```js
// Configure nucleus
const nuked = window.stardust.embed(app, {
  context: { theme: 'light' },
  types: [
    {
      name: 'combo-chart',
      load: () => Promise.resolve(window['sn-combo-chart']),
    },
  ],
  flags: { BASIC_COLOR_OPTIONS_PER_MEASURE: true },
});

// Render the combo chart
nuked.render({
  element: document.querySelector('.combo'),
  type: 'combo-chart',
  fields: ['Date.autoCalendar.YearMonth'],
  properties: {
    qHyperCubeDef: {
      qMeasures: [
        {
          qDef: {
            qDef: '=Avg(Price_Bitfinex)',
            series: { axis: 0, type: 'bar' },
            color: {
              on: true,
              paletteColor: { color: '#790C4D' },
            },
          },
        },
        {
          qDef: {
            qDef: '=Avg(Price_Gemini)',
            series: { axis: 0, type: 'bar' },
            color: {
              on: true,
              paletteColor: { color: '#0C7737' },
            },
          },
        },
        {
          qDef: {
            qDef: '=Avg(Volume_Bitfinex)',
            series: { axis: 1, type: 'line' },
            color: {
              on: true,
              paletteColor: { color: '#DB168C' },
            },
          },
        },
        {
          qDef: {
            qDef: '=Avg(Volume_Gemini)',
            series: { axis: 1, type: 'line' },
            color: {
              on: true,
              paletteColor: { color: '#16DB64' },
            },
          },
        },
      ],
    },
    dimensionAxis: {
      dock: 'near',
      axisDisplayMode: 'custom',
      maxVisibleItems: 50,
    },
    preferContinuousAxis: false,

    // Make the lines look better
    components: [
      {
        key: 'line',
        style: {
          lineThickness: 3,
          lineCurve: 'monotone',
        },
      },
    ],
  },
});
```

## Combo chart plugins

A plugin can be passed into a combo 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 and the position of the minor secondary axis title
const minorSecondaryAxisTitlePlugin = {
  info: {
    name: 'minor-secondary-axis-title-plugin',
    type: 'component-definition',
  },
  fn: ({ keys, layout }) => {
    const componentDefinition = {
      type: 'data-title',

      // Provide the same name as the exisiting component to override it
      key: keys.COMPONENT.AXIS_TITLE.MINOR.SECONDARY,
      style: {
        fontFamily: 'Tahoma, san-serif',
        fontSize: '15px',
        color: '#EC983D',
      },
    };
    return componentDefinition;
  },
};

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

// Rendering a combo chart with plugins
nuked.render({
  element: document.getElementById('object'),
  type: 'sn-combo-chart',
  fields: ['Date.autoCalendar.YearMonth', '=Avg(Price_Gemini)', '=Avg(Volume_Gemini)'],
  plugins: [minorSecondaryAxisTitlePlugin],
  properties: {
    title: 'Bitcoin Price and Trading Volume (USD) on Gemini',
  },
});
```

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: {
      MAJOR,
      MAJOR_INNER,
      MINOR: {
        PRIMARY,
        SECONDARY,
      },
    },
    COMPONENT: {
      BAR_PRIMARY,
      BAR_SECONDARY,
      AXIS: {
        MAJOR,
        TIME_INNER,
        MINOR: {
          PRIMARY,
          SECONDARY,
        },
      },
      AXIS_TITLE: {
        MAJOR,
        MINOR: {
          PRIMARY,
          SECONDARY,
        },
      },
    },
    COLLECTION: { MAIN },
  },
};
```

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

### Add new components

The new component can be a standard Picasso component
or a custom Picasso component. Here we demo a standard
reference line component.

```js
// Adding reference line at the median of the price
const medianReferenceLinePlugin = {
  info: {
    name: 'median-reference-line-plugin',
    type: 'component-definition',
  },
  fn: ({ keys, layout }) => {
    // We are only interested in data after year 2018
    const barValues = layout.qHyperCube.qDataPages[0].qMatrix
      .filter((item) => item[0].qText >= '2018')
      .map((item) => item[1].qNum);
    const value = getMedian(barValues);
    const componentDefinition = {
      key: 'median-reference-line',
      type: 'ref-line',
      lines: {
        y: [
          {
            line: {
              stroke: 'blue',
              strokeWidth: 2,
            },
            scale: keys.SCALE.MINOR.PRIMARY,
            value,
            label: {
              text: `Median price since 2018:`,
            },
          },
        ],
      },
    };
    return componentDefinition;
  },
};
```

### Modify existing components

As an example, the appearance of the bars can be
modified 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.BAR_PRIMARY` in
this example)

```js
// Modifying the look of the existing bar component
const barPlugin = {
  info: {
    name: 'bar-plugin',
    type: 'component-definition',
  },
  fn: ({ layout, keys }) => {
    const componentDefinition = {
      type: 'box',

      // Provide the same name as the exisiting bar component to override it
      key: keys.COMPONENT.BAR_PRIMARY,
      settings: {
        box: { minWidthPx: 10 },
      },
    };
    return componentDefinition;
  },
};
```

### Plugins disclaimer

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