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DataTransform

Package | mx.charts.chartClasses
Class | public class DataTransform
Inheritance | DataTransform flash.events.EventDispatcher
Subclasses | CartesianTransform, PolarTransform

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

The DataTransform object represents a portion of a chart that contains glyphs and can transform values to screen coordinates and vice versa. Each DataTransform object has a horizontal axis, a vertical axis, and a set of glyphs (background, data, and overlay) to render.

In theory, a chart can contain multiple overlaid DataTransform objects. This allows you to display a chart with multiple data sets rendered in the same area but with different ranges. For example, you might want to show monthly revenues compared to the number of units sold. If revenue was typically in millions while units was typically in the thousands, it would be difficult to render these effectively along the same range. Overlaying them in different DataTransform objects allows the end user to compare trends in the values when they are rendered with different ranges.

Charts can only contain one set of DataTransform.

Most of the time, you will use the ChartBase object, which hides the existance of the DataTransform object between the chart and its contained glyphs and axis objects. If you create your own ChartElement objects, you must understand the methods of the DataTransform class to correctly implement their element.

Public Properties

| Property | Defined By
--- | --- | ---
|  | axes : Object [read-only] The set of axes associated with this transform. | DataTransform
|  | elements : Array The elements that are associated with this transform. | DataTransform

Public Methods

| Method | Defined By
--- | --- | ---
|  | DataTransform() Constructor. | DataTransform
|  | dataChanged():void Informs the DataTransform that some of the underlying data being represented on the chart has changed. | DataTransform
|  | describeData(dimension:String, requiredFields:uint):Array Collects important displayed values for all elements associated with this data transform. | DataTransform
|  | getAxis(dimension:String):IAxis Retrieves the axis instance responsible for transforming the data dimension specified by the dimension parameter. | DataTransform
|  | invertTransform(... values):Array Transforms x and y coordinates relative to the DataTransform coordinate system into a two-dimensional value in data space. | DataTransform
|  | setAxis(dimension:String, v:IAxis):void Assigns an axis instance to a particular dimension of the transform. | DataTransform
|  | transformCache(cache:Array, xField:String, xConvertedField:String, yField:String, yConvertedField:String):void Maps a set of numeric values representing data to screen coordinates. | DataTransform

Events

| Event | Summary | Defined By
--- | --- | --- | ---
|  | transformChange | Dispatched when the transformation from data space to screen space has changed, typically either because the axes that make up the transformation have changed in some way, or the data transform itself has size. | DataTransform

Property Detail

axes | property

`axes:Object` [read-only]

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

The set of axes associated with this transform.

Implementation
`public function get axes():Object`

elements | property |

`elements:Array`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

The elements that are associated with this transform. This Array includes background, series, and overlay elements associated with the transform. This value is assigned by the enclosing chart object.

Implementation
`public function get elements():Array`
`public function set elements(value:Array):void`
Constructor Detail

DataTransform | () | Constructor

`public function DataTransform()`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Constructor.

Method Detail

dataChanged | () | method

`public function dataChanged():void`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Informs the DataTransform that some of the underlying data being represented on the chart has changed. The DataTransform generally has no knowledge of the source of the underlying data being represented by the chart, so glyphs should call this when their data changes so that the DataTransform can recalculate range scales based on their data. This does not invalidate the DataTransform, because there is no guarantee the data has changed. The axis objects (or range objects) must trigger an invalidate event.

describeData | () | method |

`public function describeData(dimension:String, requiredFields:uint):Array`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Collects important displayed values for all elements associated with this data transform. Axis instances call this method to collect the values they need to consider when auto-generating appropriate ranges. This method returns an Array of BoundedValue objects.

To collect important values for the horizontal axis of a CartesianTransform, pass 0. To collect values for the vertical axis, pass 1.

Parameters

| `dimension:String` — The dimension to collect values for.
| `requiredFields:uint` — Defines the data that are required by this transform.

Returns

| `Array` — A Array of BoundedValue objects.

getAxis | () | method |

`public function getAxis(dimension:String):IAxis`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Retrieves the axis instance responsible for transforming the data dimension specified by the `dimension` parameter. If no axis has been previously assigned, a default axis is created. The default axis for all dimensions is a LinearAxis with the `autoAdjust` property set to `false`.

Parameters

| `dimension:String` — The dimension whose axis is responsible for transforming the data.

Returns

| `IAxis` — The axis instance.

See also

mx.charts.LinearAxis

invertTransform | () | method |

`public function invertTransform(... values):Array`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Transforms x and y coordinates relative to the DataTransform coordinate system into a two-dimensional value in data space.

Parameters

| `... values` — The x and y positions (in that order).

Returns

| `Array` — An Array containing the transformed values.

setAxis | () | method |

`public function setAxis(dimension:String, v:IAxis):void`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Assigns an axis instance to a particular dimension of the transform. Axis objects are assigned by the enclosing chart object.

Parameters

| `dimension:String` — The dimension of the transform.
| `v:IAxis` — The target axis instance.

transformCache | () | method |

`public function transformCache(cache:Array, xField:String, xConvertedField:String, yField:String, yConvertedField:String):void`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Maps a set of numeric values representing data to screen coordinates. This method assumes the values are all numbers, so any non-numeric values must have been previously converted with the `mapCache()` method.

Parameters

| `cache:Array` — An array of objects containing the data values in their fields. This is also where this function will store the converted numeric values.
| `xField:String` — The field where the data values for the x axis can be found.
| `xConvertedField:String` — The field where the mapped x screen coordinate will be stored.
| `yField:String` — The field where the data values for the y axis can be found.
| `yConvertedField:String` — The field where the mapped y screen coordinate will be stored.

Event Detail

transformChange | Event

Event Object Type: `mx.events.FlexEvent`
FlexEvent.type property = `mx.events.FlexEvent.TRANSFORM_CHANGE`

Language Version : | ActionScript 3.0

Product Version : | Flex 3

Runtime Versions : | Flash Player 9, AIR 1.1

Dispatched when the transformation from data space to screen space has changed, typically either because the axes that make up the transformation have changed in some way, or the data transform itself has size.

The `FlexEvent.TRANSFORM_CHANGE` constant defines the value of the `type` property of the event object for a `transformChange` event.

The properties of the event object have the following values:

Property | Value
--- | ---
`bubbles` | false
`cancelable` | false
`currentTarget` | The Object that defines the event listener that handles the event. For example, if you use `myButton.addEventListener()` to register an event listener, myButton is the value of the `currentTarget`.
`target` | The Object that dispatched the event; it is not always the Object listening for the event. Use the `currentTarget` property to always access the Object listening for the event.

Wed Nov 15 2017, 09:50 AM +01:00