MATLAB by rudra pratap

6.4 Handle Graphics
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Understanding a vector of handles
In the previous script file, you may perhaps be confused about the use of the handle
hline. The command, hline=get (h, 'children'), gets the handles of all the children
of the current axes (specified by handle h) in a column vector hline. The vector
hline has seven elements-three handles for the three lines and four handles for the
four text objects (created by text and gtext commands) . So, how do we know
which handle is for which line or which text? The command get (hline ( i) , 'type ')
lists the type of the object whose handle is hline(i). The confusion is not clear yet.
What if hline(5), hline(6), and hline(7) are all lines? How do we know which
handle corresponds to which line? Once we know the type of the object, we can
identify its handle, among several similar object handles, by querying a more distinctive
property of the object, such as linestyle for lines and string for text
objects. For example, consider the handle vector hline given earlier. Then,
get (hline (5) ,'marker')
get (hline(6) ,'linestyle')
get (hline (1) ,'string')
get (hline(2) ,'string')
returns o for the line style,
returns -- for the line style,
returns in Taylor series for the string, and
returns First 3 terms for the string.
From this example, it should be clear that the handles of children of the axes
are listed in the stacking order of the objects, i.e., the last object added goes on the
top of the stack. Thus, the elements of the handle vector correspond to the objects
in the reverse order of their creation!
Deleting graphics objects
Any object in the graphics window can be deleted without disturbing the other
objects with the command
delete ( Ob jHand L e)
where ObjHandle is the handle of the object. We have used this command in the
script file that produced Fig. 6.13 to delete the text "linear approximation" from
the figure. We could have used delete (hline (6)) to delete the corresponding line
rather than making it invisible.
Modifying plots with PropEdit
Now that you have some understanding of Handle Graphics, object handles, and
object properties, you may like to use the point-and-click graphics editor, PropEdit.
Simply type propedi t to activate the editor. All graphics objects from the active
figure window are shown, along with their properties, in the PropEdit window. Yo u
can select a property from the list by clicking on it and then change it in the narrow
rectangle in the middle. A graphics object with a plus ( +) on its left indicates that
you can double-click on it to see its children.