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©2009 by L. Lagerstrom
Plotting Points
• A simple plot
• Graph options: axes, box, grid, title, etc.
• Compass plots
• Polar plots
• Plotting complex numbers
• Complex number rotation plot
Matlab code
Figure window display
©2009 by L. Lagerstrom
A Simple Plot
%Matlab allows us to create graphs
%that are displayed in the socalled
%Figure Window. Just as we have used
%a representative Command Window
%sidebyside with a listing of
%Matlab code, we'll do the same with
%the Figure Window (at the right).
%To plot an (x,y) point as a red
%circle, we use the plot function:
x = 5; y = 3;
figure(1)
clf
plot(x,y,'ro')
%'ro' = red circle
%The "figure(1)" opens the Figure
%Window and brings it to the front
%of all other open windows on the
%screen. The "clf" clears the Figure
%Window (in case there was a previous
%plot in it).
%Note that Matlab automatically sets
%the axis scaling, etc.
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©2009 by L. Lagerstrom
Graph Options
Obviously our simple plot leaves a lot to be desired. Before actually
doing the graph, it's useful to specify various options associated with
it, such as the range for each axis, whether a grid should be shown,
etc. If we don't specify anything, then Matlab will use certain default
values for the display of the graph. Here are some of the
customization options:
• axis([xmin xmax ymin ymax]) sets the range for the x and y axes
• axis square specifies a square graph (vs. rectangular)
• box on (or box off) specifies a box around the outside of the graph
• grid on (or grid off) specifies the display of a grid (or not)
The next slide shows these in action.
Matlab code
Figure window display
©2009 by L. Lagerstrom
Customizing the Simple Plot
%Here's a more customized plot:
x = 5; y = 3;
figure(1)
clf
plot(x,y,'ro')
axis([0 6 0 6])
axis square
box on
grid on
%Note that the axis, box, and grid
%commands should come after the plot
%command.
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Matlab code
Figure window display
©2009 by L. Lagerstrom
Adding a Title and Axis Labels
%We can add a title at the top of the
%plot and labels for each axis using
%the title, xlabel, and ylabel
%functions, as shown. Each of these
%takes a string as an input parameter.
%(Note that we also turned the box
%and grid off to see how that
%looks.)
x = 5; y = 3;
figure(1)
clf
plot(x,y,'ro')
axis([0 6 0 6])
axis square
box off
grid off
title('A Simple Plot')
xlabel('The x axis')
ylabel('The y axis')
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A Simple Plot
The x axis
The y axis
Matlab code
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 Spring '10
 Lagerstrom
 Complex number, L. Lagerstrom

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