Next: Graphics Objects, Up: Graphics Data Structures [Contents][Index]
The graphics functions use pointers, which are of class graphics_handle, in
order to address the data structures which control visual display. A
graphics handle may point to any one of a number of different base object
types and these objects are the graphics data structures themselves. The
primitive graphic object types are: figure, axes, line,
text, patch, surface, text, image, and
light.
Each of these objects has a function by the same name, and, each of these
functions returns a graphics handle pointing to an object of the corresponding
type. In addition there are several functions which operate on properties of
the graphics objects and which also return handles: the functions plot
and plot3 return a handle pointing to an object of type line, the
function subplot returns a handle pointing to an object of type axes,
the function fill returns a handle pointing to an object of type patch,
the functions area, bar, barh, contour,
contourf, contour3, surf, mesh, surfc,
meshc, errorbar, quiver, quiver3, scatter,
scatter3, stair, stem, stem3 each return a handle
to a complex data structure as documented in
Data Sources.
The graphics objects are arranged in a hierarchy:
1. The root object is returned by groot (historically, equivalent to
the handle 0). In other words, get (groot) returns the properties of
the root object.
2. Below the root are figure objects.
3. Below the figure objects are axes or hggroup objects.
4. Below the axes objects are line, text, patch,
surface, image, and light objects.
Graphics handles may be distinguished from function handles
(see Function Handles) by means of the function ishghandle.
ishghandle returns true if its argument is a handle of a graphics
object. In addition, a figure or axes object may be tested using
isfigure or isaxes respectively. To test for a specific type of
graphics handle, such as a patch or line object, use isgraphics. The
more specific test functions return true only if the argument is both a
graphics handle and of the correct type (figure, axes, specified object type).
The whos function can be used to show the object type of each currently
defined graphics handle. (Note: this is not true today, but it is, I hope,
considered an error in whos. It may be better to have whos just show
graphics_handle as the class, and provide a new function which, given a
graphics handle, returns its object type. This could generalize the ishandle()
functions and, in fact, replace them.)
The get and set commands are used to obtain and set the values of
properties of graphics objects. In addition, the get command may be
used to obtain property names.
For example, the property "type" of the graphics object pointed to by
the graphics handle h may be displayed by:
get (h, "type")
The properties and their current values are returned by get (h)
where h is a handle of a graphics object. If only the names of the
allowed properties are wanted they may be displayed by:
get (h, "").
Thus, for example:
h = figure (); get (h, "type") ans = figure get (h, ""); error: get: ambiguous figure property name ; possible matches: __gl_extensions__ dockcontrols renderer __gl_renderer__ doublebuffer renderermode __gl_vendor__ filename resize __gl_version__ graphicssmoothing resizefcn __graphics_toolkit__ handlevisibility selected __guidata__ hittest selectionhighlight __modified__ integerhandle selectiontype __mouse_mode__ interruptible sizechangedfcn __myhandle__ inverthardcopy tag __pan_mode__ keypressfcn toolbar __plot_stream__ keyreleasefcn type __rotate_mode__ menubar uicontextmenu __zoom_mode__ mincolormap units alphamap name userdata beingdeleted nextplot visible busyaction numbertitle windowbuttondownfcn buttondownfcn outerposition windowbuttonmotionfcn children paperorientation windowbuttonupfcn clipping paperposition windowkeypressfcn closerequestfcn paperpositionmode windowkeyreleasefcn color papersize windowscrollwheelfcn colormap papertype windowstyle createfcn paperunits wvisual currentaxes parent wvisualmode currentcharacter pointer xdisplay currentobject pointershapecdata xvisual currentpoint pointershapehotspot xvisualmode deletefcn position
The properties of the root figure may be displayed by:
get (groot, "").
The uses of get and set are further explained in
get, set.
Return true if prop is a property of the object obj.
obj may also be an array of objects in which case res will be a logical array indicating whether each handle has the property prop.
For plotting, obj is a handle to a graphics object. Otherwise, obj should be an instance of a class.
Next: Graphics Objects, Up: Graphics Data Structures [Contents][Index]