6.2 Miscellaneous Graphics Commands

There are many plotting functions that perform different functions in Matlab. Here is a list of some that may be particularly helpful in your work:

Function	Performs
clf	Clears the graphics window
contour	Allows you to generate a contour plot of a three dimensional object
hold	Holds the current plot so you can add to it
subplot	Allows you to put many in the same window
figure	Allows you to create multiple graphics windows
gco	GCO Get handle to current object
close	Allows you to close graphics windows
plotyy	Creates 2d plot with different y axes on 2 sides
loglog	Creates a log-log plot
semilogy/semilogx	Create semi-log plots with one coordinate on a log scale.
gtext	Plce text in a plot with the mouse
ginput	Get data using the mouse from a graph

There are also graphics functions that allow you to input information using the mouse. Two of these may be very helpful. The first one is gtext.. It was illustrated in chapter 3. Here is what the help function tells us about the function:

>> help gtext 
 
 GTEXT  Place text on a graph using a mouse. 
        GTEXT('string') displays the graph window, puts up 
        a cross-hair, and waits for a mouse button or 
        keyboard key to be pressed.  The cross-hair can be
        positioned with the mouse (or with the arrow keys on 
        some computers).  Pressing a mouse button 
        or any key writes the text string onto the graph at 
        the selected location.  See also: GINPUT 

This function can simplify the process of placing text in the graphics window to specify notes about the plot. The other function is called ginput. Help used on this second function shows:

>>  help ginput 
 
GINPUT  Graphical input from a mouse or cross-hair. 
        [X,Y] = GINPUT(N) gets N points from the graph 
        window and returns the X- and Y-coordinates in 
        length N vectors X and Y.  The cross-hair can be
        positioned using a mouse (or by using the Arrow 
        Keys on a terminal).  Data points are entered by
        pressing a mouse button or any key on the keyboard. 
        [X,Y] = GINPUT gathers an unlimited number of 
        points until the return key is pressed. 
        [X,Y,BUTTON] = GINPUT(N) returns a third argument
        BUTTON that contains a vector of integers specifying
        which mouse button was used (1,2,3... from left) or 
        ASCII numbers if a key on the keyboard was used. 
        [X,Y] = GINPUT(N,'sc') returns X and Y in screen-
        coordinates where (0.0,0.0) is the lower-left corner 
        of the screen and (1.0,1.0) is the upper-right 
        corner.  Otherwise, data-coordinates are returned. 

There are a number of uses for this function. Here is a simple modification, using ginput of the yxplot function:

Now if you execute yxploti you can add whatever message you want at the point that you designate on the screen. Here is a sample run and its plot:

>> xs=0:.1:5; 
 
>> ys=xs.*sin(xs); 
 
>> yxploti('x','xsin(x)','Pointing out the Maximum','^ Maximum',xs,ys,'c')

Figure 6.6 Use of yxploti and ginput