zeppelin/docs/development/helium/writing_visualization_transformation.md

layout	title	description	group
page	Transformations in Zeppelin Visualization	Description for Transformations	development/helium

{% include JB/setup %}

Transformations for Zeppelin Visualization

Overview

Transformations

• renders setting which allows users to set columns and
• transforms table rows according to the configured columns.

Zeppelin provides 4 types of transformations.

1. PassthroughTransformation

PassthroughTransformation is the simple transformation which does not convert original tabledata at all.

See passthrough.js

2. ColumnselectorTransformation

ColumnselectorTransformation is uses when you need N axes but do not need aggregation.

See columnselector.js

3. PivotTransformation

PivotTransformation provides group by and aggregation. Every chart using PivotTransformation has 3 axes. Keys, Groups and Values.

See pivot.js

4. AdvancedTransformation

AdvancedTransformation has more detailed options while providing existing features of PivotTransformation and ColumnselectorTransformation

• multiple sub charts
• configurable chart axes
• parameter widgets: input, checkbox, option, textarea
• parsing parameters automatically based on their types
• expand / fold axis and parameter panels
• multiple transformation methods while supporting lazy converting
• re-initialize the whole configuration based on spec hash.

Spec

AdvancedTransformation requires spec which includes axis and parameter details for charts.

Let's create 2 sub-charts called line and no-group. Each sub chart can have different axis and parameter depending on their requirements.

class AwesomeVisualization extends Visualization {
  constructor(targetEl, config) {
    super(targetEl, config)
  
    const spec = {
      charts: {
        'line': {
          transform: { method: 'object', },
          sharedAxis: false, /** set if you want to share axes between sub charts, default is `false` */
          axis: {
            'xAxis': { dimension: 'multiple', axisType: 'key', description: 'serial', },
            'yAxis': { dimension: 'multiple', axisType: 'aggregator', description: 'serial', },
            'category': { dimension: 'multiple', axisType: 'group', description: 'categorical', },
          },
          parameter: {
            'xAxisUnit': { valueType: 'string', defaultValue: '', description: 'unit of xAxis', },
            'yAxisUnit': { valueType: 'string', defaultValue: '', description: 'unit of yAxis', },
            'lineWidth': { valueType: 'int', defaultValue: 0, description: 'width of line', },
          },
        },
  
        'no-group': {
          transform: { method: 'object', },
          sharedAxis: false,
          axis: {
            'xAxis': { dimension: 'single', axisType: 'key', },
            'yAxis': { dimension: 'multiple', axisType: 'value', },
          },
          parameter: {
            'xAxisUnit': { valueType: 'string', defaultValue: '', description: 'unit of xAxis', },
            'yAxisUnit': { valueType: 'string', defaultValue: '', description: 'unit of yAxis', },
        },
      },
    }

    this.transformation = new AdvancedTransformation(config, spec)
  }
  
  ...
  
  // `render` will be called whenever `axis` or `parameter` is changed 
  render(data) {
    const { chart, parameter, column, transformer, } = data
   
    if (chart === 'line') {
      const transformed = transformer()
      // draw line chart 
    } else if (chart === 'no-group') {
      const transformed = transformer()
      // draw no-group chart 
    }
  }
}

Spec: axis

Field Name	Available Values (type)	Description
dimension	single	Axis can contains only 1 column
dimension	multiple	Axis can contains multiple columns
axisType	key	Column(s) in this axis will be used as key like in PivotTransformation. These columns will be served in column.key
axisType	aggregator	Column(s) in this axis will be used as value like in PivotTransformation. These columns will be served in column.aggregator
axisType	group	Column(s) in this axis will be used as group like in PivotTransformation. These columns will be served in column.group
axisType	(string)	Any string value can be used here. These columns will be served in column.custom
maxAxisCount (optional)	(int)	The max number of columns that this axis can contain. (unlimited if undefined)
minAxisCount (optional)	(int)	The min number of columns that this axis should contain to draw chart. (1 in case of single dimension)
description (optional)	(string)	Description for the axis.

Here is an example.

axis: {
  'xAxis': { dimension: 'multiple', axisType: 'key',  },
  'yAxis': { dimension: 'multiple', axisType: 'aggregator'},
  'category': { dimension: 'multiple', axisType: 'group', maxAxisCount: 2, valueType: 'string', },
},

Spec: sharedAxis

If you set sharedAxis: false for sub charts, then their axes are persisted in global space (shared). It's useful for when you creating multiple sub charts sharing their axes but have different parameters. For example,

• basic-column, stacked-column, percent-column
• pie and donut

Here is an example.

    const spec = {
      charts: {
        'column': {
          transform: { method: 'array', },
          sharedAxis: true,
          axis: { ... },
          parameter: { ... },
        },

        'stacked': {
          transform: { method: 'array', },
          sharedAxis: true,
          axis: { ... }
          parameter: { ... },
        },

Spec: parameter

Field Name	Available Values (type)	Description
valueType	string	Parameter which has string value
valueType	int	Parameter which has int value
valueType	float	Parameter which has float value
valueType	boolean	Parameter which has boolean value used with checkbox widget usually
valueType	JSON	Parameter which has JSON value used with textarea widget usually. defaultValue should be "" (empty string). This
description	(string)	Description of this parameter. This value will be parsed as HTML for pretty output
widget	input	Use input widget. This is the default widget (if widget is undefined)
widget	checkbox	Use checkbox widget.
widget	textarea	Use textarea widget.
widget	option	Use select + option widget. This parameter should have optionValues field as well.
optionValues	(Array)	Available option values used with the option widget

Here is an example.

parameter: {
  // string type, input widget
  'xAxisUnit': { valueType: 'string', defaultValue: '', description: 'unit of xAxis', },

  // boolean type, checkbox widget
  'inverted': { widget: 'checkbox', valueType: 'boolean', defaultValue: false, description: 'invert x and y axes', },

  // string type, option widget with `optionValues`
  'graphType': { widget: 'option', valueType: 'string', defaultValue: 'line', description: 'graph type', optionValues: [ 'line', 'smoothedLine', 'step', ], },

  // HTML in `description`
  'dateFormat': { valueType: 'string', defaultValue: '', description: 'format of date (<a href="https://docs.amcharts.com/3/javascriptcharts/AmGraph#dateFormat">doc</a>) (e.g YYYY-MM-DD)', },
 
  // JSON type, textarea widget
  'yAxisGuides': { widget: 'textarea', valueType: 'JSON', defaultValue: '', description: 'guides of yAxis ', },

Spec: transform

Field Name	Available Values (type)	Description
method	object	designed for rows requiring object manipulation
method	array	designed for rows requiring array manipulation
method	array:2-key	designed for xyz charts (e.g bubble chart)
method	drill-down	designed for drill-down charts
method	raw	will return the original tableData.rows

Whatever you specified as transform.method, the transformer value will be always function for lazy computation.

// advanced-transformation.util#getTransformer

if (transformSpec.method === 'raw') {
  transformer = () => { return rows; }
} else if (transformSpec.method === 'array') {
  transformer = () => {
    ...
    return { ... }
  }
}

Here is actual usage.

class AwesomeVisualization extends Visualization {
  constructor(...) { /** setup your spec */ }
  
  ... 
  
  // `render` will be called whenever `axis` or `parameter` are changed
  render(data) {
    const { chart, parameter, column, transformer, } = data
   
    if (chart === 'line') {
      const transformed = transformer()
      // draw line chart 
    } else if (chart === 'no-group') {
      const transformed = transformer()
      // draw no-group chart 
    }
  }
  
  ...
}