Graphical representation of data in LABVIEW MATHSCRIPT LABVIEW MATHSCRIPT provides a great variety of functions and techniques for graphical display of data. The flexibility and ease of use of LABVIEW MATHSCRIPT's plotting tools is one of its key strengths. In LABVIEW MATHSCRIPT graphs are shown in a figure window. Several figure windows can be displayed simultaneously, but only one is active. All graphing commands are applied to the active figure. The command figure(n)will activate figure number n or create a new figure indexed by n.

Tools for plotting In this section we present some of the most commonly used functions for plotting in LABVIEW MATHSCRIPT. plot- The plot and stem functions can take a large number of arguments, see help plot and help stem. For example the line type and color can easily be changed. plot(y) plots the values in vector yversus their index. plot(x,y) plots the values in vector yversus x. The plot function produces a piecewise linear graph between its data values. With enough data points it looks continuous. stem- Using stem(y)the data sequence yis plotted as stems from the x-axis terminated with circles for the data values. stem is the natural way of plotting sequences. stem(x,y) plots the data sequence y at the values specified in x. xlabel('string')- Labels the x-axis with string. ylabel('string')- Labels the y-axis with string. title('string')- Gives the plot the title string. To illustrate this consider the following example. In this example we plot the function y = x2 for x 2 [-2; 2]. x = -2:0.2:2;


	
		y = x.^2;
	
	
		
	
	
		figure(1);
	
	
		
	
	
		plot(x,y);
	
	
		
	
	
		xlabel('x');
	
	
		
	
	
		ylabel('y=x^2');
	
	
		
	
	
		title('Simple plot');
	
	
		
	
	
		figure(2);
	
	
		
	
	
	stem(x,y);
		
	
		
	
	
		xlabel('x');
	
	
		
	
	
		ylabel('y=x^2');
	
	
		
	
	
		title('Simple stem plot');
	
	This code produces the following two figures.

	
Some more commands that can be helpful when
working with plots:

hold on / off - Normally hold is off. This means that the
plot command replaces the current plot with the new one. To add a
new plot to an existing graph use 
hold on. If you want to overwrite the current plot
again, use 
hold off.


legend('plot1','plot2',...,'plot N')- The 
legend command provides an easy way to identify
individual plots when there are more than one per figure. A legend
box will be added with strings matched to the plots.


axis([xmin xmax ymin ymax])- Use the 
axis command to set the axis as you wish. Use 
axis on/off to toggle the axis on and off
respectively.


subplot(m,n,p) -Divides the figure window into 
m rows, 
n columns and selects the 
pp'th subplot as the current plot, e.g 
subplot(2,1,1) divides the figure in two and selects
the upper part. 
subplot(2,1,2) selects the lower part.


grid on/off - This command adds or removes a
rectangular grid to your plot.



	This example illustrates 
	hold, legend and axis.

	
		x = -3:0.1:3; y1 = -x.^2; y2 = x.^2;
	
	
		
	
	
		figure(1);
	




plot(x,y1);





hold on;





plot(x,y2,'--');





hold off;





xlabel('x');





ylabel('y_1=-x^2 and y_2=x^2');





legend('y_1=-x^2','y_2=x^2');





figure(2);





plot(x,y1);





hold on;





plot(x,y2,'--');





hold off;





xlabel('x');





ylabel('y_1=-x^2 and y_2=x^2');





legend('y_1=-x^2','y_2=x^2');





axis([-1 1 -10 10]);

The result is shown below.

	    
	      
	    
	    
	      
	    
	  	  



In this example we illustrate
subplot and grid.

x = -3:0.2:3; y1 = -x.^2; y2 = x.^2;








subplot(2,1,1);





plot(x,y1);





xlabel('x'); ylabel('y_1=-x^2');





grid on;





subplot(2,1,2);





plot(x,y2);





xlabel('x');





ylabel('y_2=x^2');

Now, the result is shown below.



Printing and exporting graphics
After you have created your figures you may
want to print them or export them to graphic files. In the "File"
menu use "Print" to print the figure or "Save As" to save your
figure to one of the many available graphics formats. Using these
options should be sufficient in most cases, but there are also a
large number of adjustments available by using "Export setup",
"Page Setup" and "Print Setup".





3D Graphics

We end this module on graphics with a sneak
peek into 3D plots. The new functions here are 
meshgrid and 
mesh. In the example below we see that 
meshgridproduces 
xand 
yvectors suitable for 3D plotting and that 
mesh(x,y,z) plots 
z as a function of both 
x and 
y.

	Example: Creating our first 3D plot.
	[x,y] = meshgrid(-3:.1:3);
	
	z = x.^2+y.^2;
	
	mesh(x,y,z);
	
	xlabel('x');
	
	ylabel('y');
	
	zlabel('z=x^2+y^2');
	This code gives us the following 3D plot.