mx.charts.chartClasses.DataTransform - Adobe® Flex® 4 Language Reference (Flex 4)

Package	mx.charts.chartClasses
Class	public class DataTransform
Inheritance	DataTransform EventDispatcher Object
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

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	Property		Defined By
		axes : Object [read-only] The set of axes associated with this transform.	DataTransform
		constructor : Object A reference to the class object or constructor function for a given object instance.	Object
		elements : Array The elements that are associated with this transform.	DataTransform
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object

Public Methods

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	Method		Defined By
		DataTransform() Constructor.	DataTransform
		addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event.	EventDispatcher
		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
		dispatchEvent(event:Event):Boolean Dispatches an event into the event flow.	EventDispatcher
		getAxis(dimension:String):IAxis Retrieves the axis instance responsible for transforming the data dimension specified by the dimension parameter.	DataTransform
		hasEventListener(type:String):Boolean Checks whether the EventDispatcher object has any listeners registered for a specific type of event.	EventDispatcher
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		invertTransform(... values):Array Transforms x and y coordinates relative to the DataTransform coordinate system into a two-dimensional value in data space.	DataTransform
		isPrototypeOf(theClass:Object):Boolean Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.	Object
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void Removes a listener from the EventDispatcher object.	EventDispatcher
		setAxis(dimension:String, v:IAxis):void Assigns an axis instance to a particular dimension of the transform.	DataTransform
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		toLocaleString():String Returns the string representation of this object, formatted according to locale-specific conventions.	Object
		toString():String Returns the string representation of the specified object.	Object
		transformCache(cache:Array, xField:String, xConvertedField:String, yField:String, yConvertedField:String):void Maps a set of numeric values representing data to screen coordinates.	DataTransform
		valueOf():Object Returns the primitive value of the specified object.	Object
		willTrigger(type:String):Boolean Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type.	EventDispatcher

Events

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	Summary	Defined By
activate	[broadcast event] Dispatched when the Flash Player or AIR application gains operating system focus and becomes active.	EventDispatcher
deactivate	[broadcast event] Dispatched when the Flash Player or AIR application operating loses system focus and is becoming inactive.	EventDispatcher
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.

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
property FlexEvent.type = 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.