Basics of MATLAB and Beyond

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whosName Size Bytes Classdata 128x103x9 949248 double arrayf 1x103824 double arrayt 1x9 72 double arrayth 1x128 1024 double arrayThe data consists of spectra measured at 103 frequencies, 128 arrivalangles, and 9 time steps. Let us plot the fifth time sample:colormap(flipud(gray))imagesc(f,th,data(:,:,5))axis xycolorbarxlabel(’Frequency, Hz’)ylabel(’Arrival angle, degrees’)Darker colours correspond to higher intensities. You can see two strongsources at an angle of zero degrees and at frequencies of 85 and 170 Hz.The fact that 170 = 2 × 85 might lead us to suspect that the 170 Hzsource is just the first harmonic of the 85 Hz source. Let us look at all ofthe time samples together. This time we’ll cut off the lower intensitiesby setting the minimum colour to correspond to an intensity of 5 (thisis the call to caxis in the following code). We also turn off the y-axistick labels for all but the first plot, and we make the tick marks pointoutwards: 10for i = 1:9subplot(3,9,i), imagesc(f,th,data(:,:,i)), axis xyset(gca,’tickdir’,’out’)if i == 1ylabel(’Arrival angle, degrees’)xlabel(’Frequency, Hz’)endif i>1, set(gca,’yticklabel’,[]), endcaxis([5 Inf]), title([’i_t = ’ num2str(t(i))])end10 See Handle Graphics Sections 23 and 31 (pages 63 and 107).c○ 2000 by CRC Press LLC
You can see that over the 8 time steps, the arrival direction of the soundhas changed from −45 degrees to 30 degrees, and the two sources alwayscome from the same direction, strengthening our notion that the two arein fact harmonics of the same source. Let us look at the time-frequencyand time-angle distributions of this data. The above output of the whoscommand shows that the row index of data corresponds to the differentangles, so if we calculate the mean over the rows we will be left with atime-frequency distribution:>> time_freq = mean(data);>> size(time_freq)ans =1 1039We are left with a 1 × 103 × 9 matrix of averages over the 128 arrivalangles. To plot the results we have to squeeze this to a two-dimensional103 × 9 matrix:time_freq = squeeze(mean(data));imagesc(t,f,time_freq)axis xyxlabel(’Time, s’)ylabel(’Frequency, Hz’)The frequency varies slightly with time. By averaging the rows of thedata matrix we can get a similar plot of the variation of arrival anglewith time:time_angle = squeeze(mean(data,2));imagesc(t,th,time_angle)axis xyxlabel(’Time, s’)ylabel(’Arrival angle, degrees’)29.5 Multidimensional Cell ArraysMultidimensional cell arrays are just like ordinary multidimensionalarrays, except that the cells can contain not only numbers, but vectors,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
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i =i =123136Vectorised Codematlab i
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9.1 MATLAB FormatTo save all the va
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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
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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 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: An Application of RGB ImagesTo see
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 =
Page 155 and 156: fail. One place to put variables th
Page 157 and 158: 34.7 Fast DrawingFor fast drawing o
Page 159 and 160: 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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