Matlab Graphics S. Awad, Ph.D. M. Corless, M.S.E.E. E.C.E. Department University of Michigan-Dearborn Introduction to Matlab: 2D Graphics

MatlabGraphics

S. Awad, Ph.D.

M. Corless, M.S.E.E.

E.C.E. Department

University of Michigan-Dearborn

Introduction to Matlab:

2D Graphics

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MATLAB Graphics:U of M-Dearborn ECE DepartmentIntroduction to MATLAB and its Toolboxes

2D Graphics

2D Graphics Topics Creating Two Dimensional Plots Creating Multiple Plots Using a Legend Box Customizing Axes Zoom Command Adding Text Getting Data from a Graph Sub Plotting Other 2D Features and Plot Types 2D EZPlot

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2D Graphics

» theta=[0:pi/128:2*pi]';

» y=sin(theta);

» plot(theta,y,'b.');

» xlabel('Angle in Radians');

» ylabel('Amplitude');

» title('One Period of a Sine Wave');

Two-Dimensional Plots Plot Command for 2D plots Sinewave Example:

Marker: Point

Color: Blue

Writes Title of Graph

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2D Graphics

To Disable Grid

2-D Grids

To Enable Grid

» grid on

» grid off

Grid Toggles

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2D Graphics

» theta=[0:pi/32:2*pi]';

» y=cos(theta);

» stem(theta,y, 'rx');

» xlabel('Angle in Radians');


» title('Stem Plot of Cosine Wave');

Color: Red

Marker: x

Stem Command

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2D Graphics

Clearing a Figure In case a figure already exists, the plot command

will clear the current figure window and draws a new plot.

To clear a figure use the clf command

» clf

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2D Graphics

Multiple Plots Consider the following vector pairs:

» x1=[1 2 3 4]'; y1=[4 4.1 4.2 4.3]';

(x1 and x2 have same length)

» x2=[1 2 3 4 5]'; y2=[5 5.1 5.2 5.3 5.4]';

(x2 & y2 have same length but may be different from x1 & y1)

» x3=[1 2 3 4 5 6]'; y3=[6 6.1 6.2 6.3 6.4 6.5]';

(x3 & y3 have same length but may be different from x1 & y1...)

To plot the 3 plots on the same graph

plot(x1,y1,'r',x2,y2,'xb',x3,y3,'k');

xlabel, ylabel, & title can also be put on the graph

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2D Graphics

Figure with Multiple Plotsplot(x1,y1,'r',x2,y2,'xb',x3,y3,'k');

r = color: red

xb = marker: x

color: blue

k = color: black

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2D Graphics

Plotting Using Hold hold on command to draw multiple plots on same figure

» plot(x1,y1,'r'); » hold on» plot(x2,y2,'xb')» hold on» plot(x3,y3,'k');

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2D Graphics

If x1, x2, & x3 are the same vector x:» x =[1 2 3 4 ]’;

And there are y1, y2, & y3 of same size:» y1=[1 2 3 4 ]’;

» y2=[1.2 2.2 3.2 4.2]’;

» y3=[1.4 2.4 3.4 4.4]’;

Then to plot the 3 plots at the same time» y = [ y1, y2, y3] % 3 columns

» plot( x,y );

Vectors of Same Length

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2D Graphics

Same Length Plots

3 Vectors

How to Distinguish between plots?

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2D Graphics

Legend Box To create a legend box in the upper right corner

of the plot for the previous example:

» legend('First', 'Second', 'Third' );

To move the legend, click and hold the left mouse button near the edge of the legend and drag it to the required place.

To delete the legend, use

» legend off

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2D Graphics

Placing Legend Box

Click and Drag to place Legend

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2D Graphics

Customizing Axes To set each axis minimums and maximums

» axis([ xmin xmax ymin ymax]);

To return to default settings

» axis('auto') or » axis auto

Set scaling factors for both axes to be equal» axis equal

To keep MATLAB from altering the proportions of the axes if the view is changed

» axis vis3d

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2D Graphics

Zoom Command To expand the sections of a 2-D plot use

» zoom on Click the left mouse button to expand

the area by a factor of 2 around the point under the mouse pointer

Each time you click, the plot expands

To return plot to it’s initial state» zoom out

To exit zoom mode» zoom off

Note: Turn Legend off before using zoom

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2D Graphics

Adding Text to a Graph gtext is used to place text on a graph It puts the cross-hair that follows the mouse and

waits for a click at the desired location

» gtext('These are straight lines');

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2D Graphics

Getting Data from a Graph Suppose there is a current plot on the screen

and we want to select some points from the graph and return the x & y coordinates

To do this use the ginput command

Number of Points Selected

Y-Coordinate Vector

X-Coordinate Vector

» [xp, yp] = ginput(3);

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2D Graphics

Subplots on Same Figure subplot(m,n,p) breaks the Figure window into an

m-by-n matrix of small axes & selects the p-th axes The p-th axis is numbered left to right along the top row,

second row, etc. Each subplot is a separate graph

When a particular subplot is active, it is the only subplot (or axis) that is responsive to axis, xlabel, etc. The other subplots are not affected.

To return to default mode use:

» subplot(1,1,1)

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2D Graphics

Subplot Example» subplot(2,3,1);

» title('plot 1');

» subplot(2,3,2);

» title('plot 2');

» subplot(2,3,3);

» title('plot 3');

» subplot(2,3,4);

» title('plot 4');

» subplot(2,3,5);

» title('plot 5');

» subplot(2,3,6);

» title('plot 6');

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2D Graphics

Other 2-D Features

» loglog(x,y); Plots log scale for x & y

» semilogx(x,y); X-Axis uses log scale

» semilogy(x,y); Y-Axis uses log scale

» pie(a,b); Pie Chart (a&b are vectors)

» bar(x,y); Bar Graph

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2D Graphics

Pie Chart Example» a=[0.5, 1, 1.6, 1.2, 0.8, 2.1];

» pie(a,a==max(a));

Optional logical vector

describing a slice or

slices to be pulled out

of pie chart

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2D Graphics

Bar Graph Example

» x=[-2.9:0.2:2.9];

» y=exp(-x.*x);

» bar(x,y);

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2D Graphics

» f='sin(x)';

» xmin=-2*pi;xmax=2*pi;

» ezplot(f,[xmin,xmax]);

2-D EZPlot ezplot(f) is used to plot symbolic variables f is a string or symbolic expression representing

a mathematical expression involving a single symbolic variable say ‘x’;

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2D Graphics

EZPlot Sine Example» f='sin(2*x)*exp(-x)';xmin=0;xmax=2*pi;

» ezplot(f,[xmin,xmax]);

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2D Graphics

EZPlot X2 Example» ezplot('x^2',[0,5]),grid;

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2D Graphics

EZPlot Exponential Example

» f='sin(x)*exp(-x)';

» ezplot(f,[0,10]);

» grid on;


Documents

Matlab Graphics S. Awad, Ph.D. M. Corless, M.S.E.E. E.C.E. Department University of Michigan-Dearborn Introduction to Matlab: 2D Graphics