Adobe® Flex® 4 Language Reference
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mx.charts.chartClasses 
DataTransform 
Packagemx.charts.chartClasses
Classpublic class DataTransform
InheritanceDataTransform Inheritance EventDispatcher Inheritance 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
 PropertyDefined By
  axes : Object
[read-only] The set of axes associated with this transform.
DataTransform
 Inheritedconstructor : 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
 Inheritedprototype : Object
[static] A reference to the prototype object of a class or function object.
Object
Public Methods
 MethodDefined By
  
Constructor.
DataTransform
 Inherited
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
  
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
 Inherited
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
 Inherited
Checks whether the EventDispatcher object has any listeners registered for a specific type of event.
EventDispatcher
 Inherited
Indicates whether an object has a specified property defined.
Object
  
Transforms x and y coordinates relative to the DataTransform coordinate system into a two-dimensional value in data space.
DataTransform
 Inherited
Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.
Object
 Inherited
Indicates whether the specified property exists and is enumerable.
Object
 Inherited
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
 Inherited
Sets the availability of a dynamic property for loop operations.
Object
 Inherited
Returns the string representation of this object, formatted according to locale-specific conventions.
Object
 Inherited
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
 Inherited
Returns the primitive value of the specified object.
Object
 Inherited
Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type.
EventDispatcher
Events
 Event Summary Defined By
 Inherited[broadcast event] Dispatched when the Flash Player or AIR application gains operating system focus and becomes active.EventDispatcher
 Inherited[broadcast event] Dispatched when the Flash Player or AIR application operating loses system focus and is becoming inactive.EventDispatcher
  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

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:

PropertyValue
bubblesfalse
cancelablefalse
currentTargetThe 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.
targetThe 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.