Basics of MATLAB and Beyond

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clfgplot(A,[x y])axis off(Try zooming in on this plot by typing zoom and dragging the mouse.)The adjacency matrix here (A) is a 4251×4253 sparse matrix with 12,289non-zero elements, occupying 164 kB of storage. A full matrix of thissize would require 145 MB.(From now on in this book, the clf command will be omitted fromthe examples; you will need to supply your own clfs where appropriate.)25.2 Example: Communication NetworkSuppose we have a communications network of nodes connected by wiresthat we want to represent using sparse matrices. Let us suppose thenodes are 10 equispaced points around the circumference of a circle.dt = 2*pi/10;t = dt:dt:10*dt;x = cos(t)’;y = sin(t)’;plt(x,y)axis equal offfor i = 1:10text(x(i),y(i),int2str(i))endWe want the communications channels to go between each node and itstwo second-nearest neighbours, as well as to its diametrically oppositenode. For example, node 1 should connect to nodes 3, 6, and 9; node 2should connect to nodes 4, 7, and 10; and so on. The function spdiagsis used on the following to put the elements of e along the second, fifth,and eighth diagonals of the (sparse) matrix A. If you look at the help forspdiags, you should be able to follow how these statements define theconnection matrix we want. First we define the connection matrix:e = ones(10,1);A = spdiags(e,2,10,10) + ...spdiags(e,5,10,10) + ...spdiags(e,8,10,10);A = A + A’;Now do the plot:c○ 2000 by CRC Press LLC
subplot(221)spy(A)subplot(222)gplot(A,[x y])axis equal offfor i = 1:10text(x(i),y(i),int2str(i))endThe plots show the sparse node-connection matrix on the left and thephysical connection on the right.Exercise 7 Repeat this communications example for the case of100 nodes around the circle. Then try changing the connectionmatrix. (Answer on page 187.)26 Text StringsA string is an array of characters. For example, these are strings:’hello’, ’John Smith’, and ’12’. The last one is a string, not thenumber 12, because it is surrounded by quotes. matlab represents charactersas their ascii values. You can convert between ascii values andthe characters they represent using the double and char commands:>> alph = ’ABCDE’alph =ABCDE>> num = double(alph)num =65 66 67 68 69>> char(num)ans =ABCDE>> char(num+5)ans =FGHIJThe double command converts its argument to double precision values,the default matlab format.To get a quote character in a string use two quotes in succession:>> str = ’you’’re the one’c○ 2000 by CRC Press LLC
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BASICS OFMATLAB®and Beyondc○ 200
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Library of Congress Cataloging-in-P
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typing pwd (print working directory
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ContentsIBasics of MATLAB1 First St
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20 Time-Frequency Analysis21 Line A
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39Answers to Exercises (Part I)40 A
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Set → Getting Started with MATLAB
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1.5 The Colon OperatorTo generate a
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matlab will recall the last command
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a = zeros(2,3)a =0 0 00 0 0>> b = o
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[a a(a)]ans =1 2 3 1 4 74 5 6 2 5 8
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a + bans =11 3344 6677 993.8 Transp
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4.2 Adding PlotsWhen you issue a pl
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x = [[1 2 3 4]’ [2 3 4 5]’ [3 4
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4.7 AxesSo far we have allowed matl
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v =1122>> v*uans =1 2 0 11 2 0 12 4
Page 34 and 35: max returns a vector containing the
Page 36 and 37: s = 100*spiral(3)s =700 800 900600
Page 38 and 39: We can plot the surface z as a func
Page 40 and 41: The contour function plots the cont
Page 42 and 43: m = gray(8);colormap(m)imagesc(1:10
Page 44 and 45: hold onplot3(x(ind),y(ind),z(ind),
Page 46 and 47: z = 5*ones(3,3)z =5 5 55 5 55 5 5>>
Page 48 and 49: contour(x,y,z,30);You may have noti
Page 50 and 51: variables that are local to themsel
Page 52 and 53: SwitchThe basic form of a switch st
Page 54 and 55: i =i =123136Vectorised Codematlab i
Page 56 and 57: 9.1 MATLAB FormatTo save all the va
Page 58 and 59: 11 StartupEach time you start matla
Page 60 and 61: Where p i is the population for yea
Page 62 and 63: NaNs by leaving them off the plot.
Page 64 and 65: clfpolar(t,gdb)In this case you mus
Page 66 and 67: -0.5000-0.3750-0.2500-0.125000.1250
Page 68 and 69: the periodograms of the blocks, and
Page 70 and 71: plot(y(1:1000))axis([0 1000 -5 5])z
Page 72 and 73: comet(x,y)(You can get a three-dime
Page 74 and 75: By clicking within the panner box a
Page 76 and 77: x = linspace(-1,1,8192);Fs = 1000;y
Page 78 and 79: 23.3 Graphical Object Hierarchymatl
Page 80 and 81: Now we need to get the handles of a
Page 82 and 83: Beyond the BasicsPreludeThis part o
Page 86 and 87: str =you’re the one>> str = ’
Page 88 and 89: strrep(str,’go’,’am’)ans =I
Page 90 and 91: ans =3.14159e+100Some additional te
Page 92 and 93: eval(str)v =1 2 3 4 5The eval(str)
Page 94 and 95: Inline objects, like every other ma
Page 96 and 97: a(1,1) = {[1 2 3]}a =[1x3double]or>
Page 98 and 99: t = {’help’ spiral(3) ; eye(2)
Page 101 and 102: meteo.Temperatureans =24ans =19.000
Page 103 and 104: 3 >> a = [1 2 ;4 5 6;7 8 9]a =1 2 3
Page 105 and 106: [x,y] = meshgrid(1:5,1:3)x =1 2 3 4
Page 107 and 108: ans(:,:,2) =999And to sum over “p
Page 109 and 110: An Application of RGB ImagesTo see
Page 111 and 112: You can see that over the 8 time st
Page 113 and 114: name>> staff(2,1,2).name(5:9)ans =B
Page 115 and 116: q =7 8 96 1 25 4 3>> save saved_dat
Page 117 and 118: fid = fopen(’asc.dat’);The fope
Page 119 and 120: display and the enclosed area is th
Page 121 and 122: MarkerEdgeColor = auto(and so on)In
Page 123 and 124: text(-.7,f(-.7),’f(X)’)But we h
Page 125 and 126: plt(x,f(x/2),’--’)Let us try ca
Page 127 and 128: Example: findobjThe findobj command
Page 129 and 130: 3. Add the property you want to set
Page 131 and 132: is numbered from top to bottom. The
Page 133 and 134: axis ijUsually images like this do
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32.2 Tick Marks and Labelsmatlab’
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clfaxes(’pos’,[.2 .1 .7 .4])x =
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property to [0 top] in the call to
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object’s HorizontalAlignment and
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the required symbols. The m-file ti
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1. Use graphical elements that serv
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uicontrol(’Callback’,’ezplot(
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uicontrol(’Pos’,[110 280 60 19]
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’String’,’0.5’,’Style’,
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function exradio(action)if nargin =
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fail. One place to put variables th
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34.7 Fast DrawingFor fast drawing o
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controlled by guide and which are a
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InvertHardcopy: [ {on} | off ]Paper
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Another option is to use an image f
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yur is the y coordinate of the uppe
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\end{center}\caption{This is the fi
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x 294x1 ...y 294x1 ...z 294x1 ...Gr
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diagram. Such a triangular grid can
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xt = x([1 9 10 1]);yt = y([1 9 10 1
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x = [0 0 .5 0.5 .5 1 11 .5 .5 .5];y
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fac2 = [1 2 61 6 31 4 61 6 5];The r
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t = linspace(0,2*pi,20);x = cos(t);
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N = 20;dt = 2*pi/N;t = 0:dt:(N-1)*d
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colouring of the sphere itself. To
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material dullThe default is materia
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time taken by this routine to calcu
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first row of a by taking the column
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38.3 Debuggingmatlab has a suite of
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10: y = linspace(ycentre - L,ycentr
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We change variables:p ′ = C + Bx.
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Exercise 6 (Page 59)You can generat
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33 ! 36 $ 39 ’ 42 * 45 - 48 034 "
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R = 1; N = 200;[x,y] = meshgrid(lin
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(The plot might take a few seconds
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% Reproduce the layers at the diffe
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