MATLAB Function Reference

Quivergroup Properties

You can set and query graphics object properties using the set and get commands or the Property Editor (propertyeditor).

Note that you cannot define default properties for areaseries objects.

See Plot Objects for more information on quivergroup objects.

Quivergroup Property Descriptions

This section provides a description of properties. Curly braces { } enclose default values.

Autoscale arrow length. Based on average spacing in the x and y directions, AutoScale scales the arrow length to fit within the grid-defined coordinate data and keeps the arrows from overlapping. After autoscaling, quiver applies the AutoScaleFactor to the arrow length.

User-specified scale factor. When AutoScale is on, the quiver function applies this user-specified autoscale factor to the arrow length. A value of 2 doubles the length of the arrows; 0.5 halves the length.

This object is being deleted. The BeingDeleted property provides a mechanism that you can use to determine if objects are in the process of being deleted. MATLAB sets the BeingDeleted property to on when the object's delete function callback is called (see the DeleteFcn property). It remains set to on while the delete function executes, after which the object no longer exists.

For example, an object's delete function might call other functions that act on a number of different objects. These functions might not need to perform actions on objects that are going to be deleted, and therefore can check the object's BeingDeleted property before acting.

Callback routine interruption. The BusyAction property enables you to control how MATLAB handles events that potentially interrupt executing callbacks. If there is a callback function executing, callbacks invoked subsequently always attempt to interrupt it.

If the Interruptible property of the object whose callback is executing is set to on (the default), then interruption occurs at the next point where the event queue is processed. If the Interruptible property is off, the BusyAction property (of the object owning the executing callback) determines how MATLAB handles the event. The choices are

• cancel -- Discard the event that attempted to execute a second callback routine.
• queue -- Queue the event that attempted to execute a second callback routine until the current callback finishes.

Button press callback function. A callback that executes whenever you press a mouse button while the pointer is over the quivergroup object.

This property can be

• A string that is a valid MATLAB expression
• The name of an M-file
• A function handle

The expression executes in the MATLAB workspace.

See Function Handle Callbacks for information on how to use function handles to define the callbacks.

Children of the quivergroup object. An array containing the handles of all line objects parented to the quivergroup object (whether visible or not).

Note that if a child object's HandleVisibility property is set to callback or off, its handle does not show up in the quiver Children property unless you set the Root ShowHiddenHandles property to on:

• set(0,'ShowHiddenHandles','on')
  

Clipping mode. MATLAB clips quiver plots to the axes plot box by default. If you set Clipping to off, arrows might be displayed outside the axes plot box.

Color of arrows. A three-element RGB vector or one of the MATLAB predefined names, specifying the arrow color. See the ColorSpec reference page for more information on specifying color. For example, the following statement shows the arrow color set to blue.

• h = quiver(u,v,'Color','b');
  

Callback routine executed during object creation. This property defines a callback that executes when MATLAB creates a quivergroup object. You must specify the callback during the creation of the object. For example,

• quiver(u,v,'CreateFcn',@CallbackFcn)
  

where @CallbackFcn is a function handle that references the callback function.

MATLAB executes this routine after setting all other quivergroup properties. Setting this property on an existing quivergroup object has no effect.

The handle of the object whose CreateFcn is being executed is accessible only through the root CallbackObject property, which you can query using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

Callback executed during object deletion. A callback that executes when the quivergroup object is deleted (e.g., this might happen when you issue a delete command on the quivergroup object, its parent axes, or the figure containing it). MATLAB executes the callback before destroying the object's properties so that the callback routine can query these values.

The handle of the object whose DeleteFcn is being executed is accessible only through the Root CallbackObject property, which can be queried using gcbo.

See Function Handle Callbacks for information on how to use function handles to define the callback function.

See the BeingDeleted property for related information.

Label used by plot legends. The legend and the plot browser use this text for labels for any quivergroup objects appearing in these legends.

Erase mode. This property controls the technique MATLAB uses to draw and erase quiver child objects (the lines used to construct the arrows). Alternative erase modes are useful for creating animated sequences, where control of the way individual objects are redrawn is necessary to improve performance and obtain the desired effect.

• normal -- Redraw the affected region of the display, performing the three-dimensional analysis necessary to ensure that all objects are rendered correctly. This mode produces the most accurate picture, but is the slowest. The other modes are faster but do not perform a complete redraw and are therefore less accurate.
• none -- Do not erase objects when they are moved or destroyed. While the objects are still visible on the screen after erasing with EraseMode none, you cannot print these objects because MATLAB stores no information about their former locations.
• xor-- Draw and erase the object by performing an exclusive OR (XOR) with each pixel index of the screen behind it. Erasing the object does not damage the color of the objects behind it. However, the color of the erased object depends on the color of the screen behind it and it is correctly colored only when it is over the axes background color (or the figure background color if the axes Color property is set to none). That is, it isn't erased correctly if there are objects behind it.
• background -- Erase the graphics objects by redrawing them in the axes background color, (or the figure background color if the axes Color property is set to none). This damages other graphics objects that are behind the erased object, but the erased object is always properly colored.

Printing with Nonnormal Erase Modes

MATLAB always prints figures as if the EraseMode of all objects is normal. This means graphics objects created with EraseMode set to none, xor, or background can look different on screen than on paper. On screen, MATLAB might mathematically combine layers of colors (e.g., performing an XOR operation on a pixel color and the pixel behind it) and ignore three-dimensional sorting to obtain greater rendering speed. However, these techniques are not applied to the printed output.

Set the axes background color with the axes Color property. Set the figure background color with the figure Color property.

You can use the MATLAB getframe command or other screen capture applications to create an image of a figure containing nonnormal mode objects.

Control access to object's handle by command-line users and GUIs. This property determines when an object's handle is visible in its parent's list of children. HandleVisibility is useful for preventing command-line users from accidentally accessing the quivergroup object.

• on -- Handles are always visible when HandleVisibility is on.
• callback -- Setting HandleVisibility to callback causes handles to be visible from within callback routines or functions invoked by callback routines, but not from within functions invoked from the command line. This provides a means to protect GUIs from command-line users, while allowing callback routines to have access to object handles.
• off -- Setting HandleVisibility to off makes handles invisible at all times. This might be necessary when a callback invokes a function that might potentially damage the GUI (such as evaluating a user-typed string) and so temporarily hides its own handles during the execution of that function.

Functions Affected by Handle Visibility

When a handle is not visible in its parent's list of children, it cannot be returned by functions that obtain handles by searching the object hierarchy or querying handle properties. This includes get, findobj, gca, gcf, gco, newplot, cla, clf, and close.

Properties Affected by Handle Visibility

When a handle's visibility is restricted using callback or off, the object's handle does not appear in its parent's Children property, figures do not appear in the root's CurrentFigure property, objects do not appear in the root's CallbackObject property or in the figure's CurrentObject property, and axes do not appear in their parent's CurrentAxes property.

Overriding Handle Visibility

You can set the root ShowHiddenHandles property to on to make all handles visible regardless of their HandleVisibility settings (this does not affect the values of the HandleVisibility properties). See also findall.

Handle Validity

Handles that are hidden are still valid. If you know an object's handle, you can set and get its properties and pass it to any function that operates on handles.

Selectable by mouse click. HitTest determines whether the quivergroup object can become the current object (as returned by the gco command and the figure CurrentObject property) as a result of a mouse click on the line objects that compose the quiver plot. If HitTest is off, clicking the quivergroup object selects the object below it (which is usually the axes containing it).

Select quivergroup object on arrows or extent of graph. This property enables you to select quivergroup objects in two ways:

• Select by clicking quiver arrows (default).
• Select by clicking anywhere in the extent of the quiver plot.

When HitTestArea is off, you must click the quiver lines (excluding the base line) to select the quivergroup object. When HitTestArea is on, you can select the quivergroup object by clicking anywhere within the extent of the graph (i.e., anywhere within a rectangle that encloses all the arrows).

Callback routine interruption mode. The Interruptible property controls whether a quivergroup object callback can be interrupted by subsequently invoked callbacks.

Only callbacks defined for the ButtonDownFcn property are affected by the Interruptible property. MATLAB checks for events that can interrupt a callback only when it encounters a drawnow, figure, getframe, or pause command in the routine. See the BusyAction property for related information.

Setting Interruptible to on allows any graphics object's callback to interrupt callback routines originating from a quiver property. Note that MATLAB does not save the state of variables or the display (e.g., the handle returned by the gca or gcf command) when an interruption occurs.

Line style. This property specifies the line style used for the quiver arrows. Available line styles are shown in the following table.

Symbol	Line Style
-	Solid line (default)
--	Dashed line
:	Dotted line
-.	Dash-dot line
none	No line

You can use LineStyle none when you want to place a marker at each point but do not want the points connected with a line (see the Marker property).

Width of the quiver arrows. Specify this value in points (1 point = ¹/₇₂ inch). The default LineWidth is 0.5 points.

Marker symbol. The Marker property specifies the type of markers that are displayed at the x- and y-coordinates. You can set values for the Marker property independently from the LineStyle property. Supported markers include those shown in the following table.

Marker Specifier	Description
+	Plus sign
o	Circle
*	Asterisk
.	Point
x	Cross
s	Square
d	Diamond
^	Upward-pointing triangle
v	Downward-pointing triangle
>	Right-pointing triangle
<	Left-pointing triangle
p	Five-pointed star (pentagram)
h	Six-pointed star (hexagram)
none	No marker (default)

Marker edge color. The color of the marker or the edge color for filled markers (circle, square, diamond, pentagram, hexagram, and the four triangles). ColorSpec defines the color to use. none specifies no color, which makes nonfilled markers invisible. auto sets MarkerEdgeColor to the same color as the quiver Color property.

Marker face color. The fill color for markers that are closed shapes (circle, square, diamond, pentagram, hexagram, and the four triangles). ColorSpec defines the color to use. none makes the interior of the marker transparent, allowing the background to show through. auto sets the fill color to the axes color, or to the figure color, if the axes Color property is set to none (which is the factory default for axes).

Marker size. A scalar specifying the size of the marker in points. The default value for MarkerSize is 6 points (1 point = 1/72 inch). Note that MATLAB draws the point marker (specified by the '.' symbol) at one-third the specified size.

Maximum size of arrowhead. A value determining the maximum size of the arrowhead relative to the length of the arrow.

Parent of quivergroup object. This property contains the handle of the quivergroup object's parent object. The parent of a quivergroup object is the axes, hggroup, or hgtransform object that contains it.

See Objects That Can Contain Other Objects for more information on parenting graphics objects.

Is object selected? When you set this property to on, MATLAB displays selection handles at the corners and midpoints if the SelectionHighlight property is also on (the default). You can, for example, define the ButtonDownFcn callback to set this property to on, thereby indicating that the quivergroup object is selected.

Objects are highlighted when selected. When the Selected property is on, MATLAB indicates the selected state by drawing selection handles on the arrows. When SelectionHighlight is off, MATLAB does not draw the handles.

Display arrowheads on vectors. When this property is on, MATLAB draws arrowheads on the vectors displayed by quiver. When you set this property to off, quiver draws the vectors as lines without arrowheads.

User-specified object label. The Tag property provides a means to identify graphics objects with a user-specified label. This is particularly useful when you are constructing interactive graphics programs that would otherwise need to define object handles as global variables or pass them as arguments between callbacks.

For example, you might create a quivergroup object and set the Tag property:

• t = quiver(u,v,'Tag','quiver1')
  

When you want to access the quivergroup object, you can use findobj to find the object's handle. The following statement changes the Color property of the object whose Tag is quiver1.

• set(findobj('Tag','quiver1'),'Color','red')
  

Type of graphics object. This property contains a string that identifies the class of the graphics object. For stem objects, Type is 'hggroup'. This statement finds all the hggroup objects in the current axes.

• t = findobj(gca,'Type','hggroup');
  

Associate a context menu with the quivergroup object. Assign this property the handle of a uicontextmenu object created in the quivergroup object's parent figure. Use the uicontextmenu function to create the context menu. MATLAB displays the context menu whenever you right-click over the extent of the quivergroup object.

User-specified data. This property can be any data you want to associate with the quivergroup object (including cell arrays and structures). The quivergroup object does not set values for this property, but you can access it using the set and get functions.

Visibility of quivergroup object and its children. By default, stem object visibility is on. This means all children of the quivergroup object are visible unless the child object's Visible property is set to off. Setting a quivergroup object's Visible property to off also makes its children invisible.

One dimension of 2-D or 3-D vector components. UData, VData, and WData, together specify the components of the vectors displayed as arrows in the quiver graph. For example, the first vector is defined by components UData(1),VData(1),WData(1).

Link UData to MATLAB variable. Set this property to a MATLAB variable that, by default, is evaluated in the base workspace to generate the UData.

MATLAB reevaluates this property only when you set it. Therefore, a change to workspace variables appearing in an expression does not change UData.

You can use the refreshdata function to force an update of the object's data. refreshdata also enables you to specify that the data source variable be evaluated in the workspace of a function from which you call refreshdata.

See the refreshdata reference page for more information.

Note    If you change one data source property to return data of a different dimension, you might cause the function to generate a warning and not render the graph until you have changed all data source properties to appropriate values.

One dimension of 2-D or 3-D vector components. UData, VData and WData (for 3-D) together specify the components of the vectors displayed as arrows in the quiver graph. For example, the first vector is defined by components UData(1),VData(1),WData(1).

Link VData to MATLAB variable. Set this property to a MATLAB variable that, by default, is evaluated in the base workspace to generate the VData.

MATLAB reevaluates this property only when you set it. Therefore, a change to workspace variables appearing in an expression does not change VData.

You can use the refreshdata function to force an update of the object's data. refreshdata also enables you to specify that the data source variable be evaluated in the workspace of a function from which you call refreshdata.

See the refreshdata reference page for more information.

Note    If you change one data source property to return data of a different dimension, you might cause the function to generate a warning and not render the graph until you have changed all data source properties to appropriate values.

One dimension of 2-D or 3-D vector components. UData, VData and WData (for 3-D) together specify the components of the vectors displayed as arrows in the quiver graph. For example, the first vector is defined by components UData(1),VData(1),WData(1).

Link WData to MATLAB variable. Set this property to a MATLAB variable that, by default, is evaluated in the base workspace to generate the WData.

MATLAB reevaluates this property only when you set it. Therefore, a change to workspace variables appearing in an expression does not change WData.

You can use the refreshdata function to force an update of the object's data. refreshdata also enables you to specify that the data source variable be evaluated in the workspace of a function from which you call refreshdata.

See the refreshdata reference page for more information.

Note    If you change one data source property to return data of a different dimension, you might cause the function to generate a warning and not render the graph until you have changed all data source properties to appropriate values.

X-axis coordinates of arrows. The quiver function draws an individual arrow at each x-axis location in the XData array. XData can be either a matrix equal in size to all other data properties or for 2-D, a vector equal in length to the number of columns in UData or VData. That is, length(XData) == size(UData,2).

If you do not specify XData (i.e., the input argument X), the quiver function uses the indices of UData to create the quiver graph. See the XDataMode property for related information.

Use automatic or user-specified x-axis values. If you specify XData (by setting the XData property or specifying the input argument X), the quiver function sets this property to manual.

If you set XDataMode to auto after having specified XData, the quiver function resets the x tick-mark labels to the indices of the U, V, and W data, overwriting any previous values.

Link XData to MATLAB variable. Set this property to a MATLAB variable that, by default, is evaluated in the base workspace to generate the XData.

MATLAB reevaluates this property only when you set it. Therefore, a change to workspace variables appearing in an expression does not change XData.

You can use the refreshdata function to force an update of the object's data. refreshdata also enables you to specify that the data source variable be evaluated in the workspace of a function from which you call refreshdata.

See the refreshdata reference page for more information.

Note    If you change one data source property to return data of a different dimension, you might cause the function to generate a warning and not render the graph until you have changed all data source properties to appropriate values.

Y-axis coordinates of arrows. The quiver function draws an individual arrow at each y-axis location in the YData array. YData can be either a matrix equal in size to all other data properties or for 2-D, a vector equal in length to the number of rows in UData or VData. That is, length(YData) == size(UData,1).

If you do not specify YData (i.e., the input argument Y), the quiver function uses the indices of VData to create the quiver graph. See the YDataMode property for related information.

The input argument y in the quiver function calling syntax assigns values to YData.

Use automatic or user-specified y-axis values. If you specify YData (by setting the YData property or specifying the input argument Y), MATLAB sets this property to manual.

If you set YDataMode to auto after having specified YData, MATLAB resets the y tick-mark labels to the indices of the U, V, and W data, overwriting any previous values.

Link YData to MATLAB variable. Set this property to a MATLAB variable that, by default, is evaluated in the base workspace to generate the YData.

MATLAB reevaluates this property only when you set it. Therefore, a change to workspace variables appearing in an expression does not change YData.

You can use the refreshdata function to force an update of the object's data. refreshdata also enables you to specify that the data source variable be evaluated in the workspace of a function from which you call refreshdata.

See the refreshdata reference page for more information.

Note    If you change one data source property to a variable that contains data of a different dimension, you might cause the function to generate a warning and not render the graph until you have changed all data source properties to appropriate values.

Z-axis coordinates of arrows. The quiver function draws an individual arrow at each z-axis location in the ZData array. ZData must be a matrix equal in size to XData and YData.

The input argument z in the quiver3 function calling syntax assigns values to ZData.

quiver3

qz

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