Basics of MATLAB and Beyond

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a(:,:,3) =3 3 33 3 33 3 3Indexing for multidimensional arrays works in the same way as twodimensionalarrays;>> a(2,:,1)ans =4 5 6>> a(2,:,2)ans =8 10 12>> a(2,:,:)ans(:,:,1) =4 5 6ans(:,:,2) =8 10 12ans(:,:,3) =3 3 3Data can be removed from multidimensional arrays by using the emptymatrix:>> a(:,:,2) = []a(:,:,1) =1 2 34 5 67 8 9a(:,:,2) =3 3 33 3 33 3 3Elements can be columnarly extracted from multidimensional arrays inthe same way as they are from two-dimensional arrays:>> a(:)’ans =Columns 1 through 121 4 7 2 5 8 3 6 9 3 3 3Columns 13through 183 3 3 3 3 329.1 Generating Multidimensional GridsThe function meshgrid can be used to create matrices representingevenly-spaced grids of points.c○ 2000 by CRC Press LLC
[x,y] = meshgrid(1:5,1:3)x =1 2 3 4 51 2 3 4 51 2 3 4 5y =1 1 1 1 12 2 2 2 23 3 3 3 3>> clf>> plt(x,y,’o’)>> axis([0.9 5 0.9 3])Such matrices can be used, for example, as variables in functions of xand y:[x,y] = meshgrid(linspace(0,5),linspace(-10,10));r = sqrt(x.^2 + y.^2);contour(x,y,r)axis equalaxis([-10 10 -10 10])(More detail on the axis command can be found on page 119.) Themeshgrid function can be used to produce three-dimensional grids,returning three-dimensional arrays that can be used in an analogousmanner. To go to more than three dimensions, you can use the functionndgrid. The following example of a three-dimensional volume visualisationis taken from the help entry for ndgrid:[x1,x2,x3] = ndgrid(-2:.2:2, -2:.25:2, -2:.16:2);z = x2 .* exp(-x1.^2 - x2.^2 - x3.^2);slice(x2,x1,x3,z,[-1.2 .8],[], -.2)view(-24,28)Exercise 12 What is the difference between the outputs ofmeshgrid and ndgrid when generating grid matrices of less thanfour dimensions? Why this difference? (Answer on page 189.)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
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max returns a vector containing the
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s = 100*spiral(3)s =700 800 900600
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We can plot the surface z as a func
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The contour function plots the cont
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m = gray(8);colormap(m)imagesc(1:10
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hold onplot3(x(ind),y(ind),z(ind),
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z = 5*ones(3,3)z =5 5 55 5 55 5 5>>
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contour(x,y,z,30);You may have noti
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variables that are local to themsel
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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 84 and 85: clfgplot(A,[x y])axis off(Try zoomi
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: 3 >> a = [1 2 ;4 5 6;7 8 9]a =1 2 3
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
Page 135 and 136: 32.2 Tick Marks and Labelsmatlab’
Page 137 and 138: clfaxes(’pos’,[.2 .1 .7 .4])x =
Page 139 and 140: property to [0 top] in the call to
Page 141 and 142: object’s HorizontalAlignment and
Page 143 and 144: the required symbols. The m-file ti
Page 145 and 146: 1. Use graphical elements that serv
Page 147 and 148: uicontrol(’Callback’,’ezplot(
Page 149 and 150: uicontrol(’Pos’,[110 280 60 19]
Page 151 and 152: ’String’,’0.5’,’Style’,
Page 153 and 154: 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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