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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

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 2 2D Graphics Topics n Creating Two Dimensional Plots Creating Two Dimensional Plots n Creating Multiple Plots Creating Multiple Plots n Using a Legend Box Using a Legend Box n Customizing Axes Customizing Axes n Zoom Command Zoom Command n Adding Text Adding Text n Getting Data from a Graph Getting Data from a Graph n Sub Plotting Sub Plotting n Other 2D Features and Plot Types Other 2D Features and Plot Types n 2D EZPlot 2D EZPlot

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 3 » 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 n Sinewave Example: Marker: Point Color: Blue Writes Title of Graph

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 4 To Disable Grid 2-D Grids To Enable Grid » grid on » grid off Grid Toggles

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 5 » theta=[0:pi/32:2*pi]'; » y=cos(theta); » stem(theta,y, 'rx'); » xlabel('Angle in Radians'); » ylabel('Amplitude'); » title('Stem Plot of Cosine Wave'); Color: Red Marker: x Stem Command

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 6 Clearing a Figure n 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 7 Multiple Plots n 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...) n To plot the 3 plots on the same graph plot(x1,y1,'r',x2,y2,'xb',x3,y3,'k'); n xlabel, ylabel, & title can also be put on the graph

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 8 Figure with Multiple Plots plot(x1,y1,'r',x2,y2,'xb',x3,y3,'k'); r =color: red xb = marker: x color: blue k = color: black

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 9 Plotting Using Hold hold on command to draw multiple plots on same figure n » plot(x1,y1,'r'); n » hold on n » plot(x2,y2,'xb') n » hold on n » plot(x3,y3,'k');

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 10 n If x1, x2, & x3 are the same vector x: » x =[1 2 3 4 ]’; n 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]’; n 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 11 Same Length Plots n 3 Vectors n How to Distinguish between plots?

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 12 Legend Box n To create a legend box in the upper right corner of the plot for the previous example: » legend('First', 'Second', 'Third' ); n To move the legend, click and hold the left mouse button near the edge of the legend and drag it to the required place. n To delete the legend, use » legend off

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 13 Placing Legend Box n Click and Drag to place Legend

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 14 Customizing Axes n To set each axis minimums and maximums » axis([ xmin xmax ymin ymax]); n To return to default settings » axis('auto') or » axis auto n Set scaling factors for both axes to be equal » axis equal n To keep MATLAB from altering the proportions of the axes if the view is changed » axis vis3d

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 15 Zoom Command n To expand the sections of a 2-D plot use » zoom on n Click the left mouse button to expand the area by a factor of 2 around the point under the mouse pointer n Each time you click, the plot expands n To return plot to it’s initial state » zoom out n To exit zoom mode » zoom off Note: Turn Legend off before using zoom

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 16 Adding Text to a Graph gtext is used to place text on a graph n 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 17 Getting Data from a Graph n 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 18 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 n The p-th axis is numbered left to right along the top row, second row, etc. n 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. n To return to default mode use: » subplot(1,1,1)

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 19 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 20 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 21 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 22 Bar Graph Example » x=[-2.9:0.2:2.9]; » y=exp(-x.*x); » bar(x,y);

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 23 » 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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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 24 EZPlot Sine Example » f='sin(2*x)*exp(-x)';xmin=0;xmax=2*pi; » ezplot(f,[xmin,xmax]);

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 25 EZPlot X 2 Example » ezplot('x^2',[0,5]),grid;

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MATLAB Graphics: U of M-Dearborn ECE Department Introduction to MATLAB and its Toolboxes 2D Graphics 26 EZPlot Exponential Example » f='sin(x)*exp(-x)'; » ezplot(f,[0,10]); » grid on; » ylabel('Amplitude');

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