Basics of MATLAB and Beyond

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xcentre = -0.6;ycentre = 0;L = 1.5;x = linspace(xcentre - L,xcentre + L,N);y = linspace(ycentre - L,ycentre + L,N);[X,Y] = meshgrid(x,y);Z = X + i*Y;Z0 = Z;for k = 1:50;Z = Z.^2 + Z0;endind1 = find(isnan(Z));ind2 = find(~isnan(Z));Z(ind1) = 1;Z(ind2) = 0;contour(x,y,abs(Z),[.5 .5])grid;boxaxis equal offYou must tell the profile command which function you want to lookat. The format of this command changed between matlab versions 5.2and 5.3.Profile in MATLAB 5.2Initiate the profiler in matlab version 5.2 by typing:profile mandelbrotNow go ahead and run the function:mandelbrotTo see where matlab spent most of its time, type:>> profile reportTotal time in "mandelbrot.m": 30.12 seconds100% of the total time was spent on lines:[15 21 12 18 17 19 11 20 22 16 ]c○ 2000 by CRC Press LLC
10: y = linspace(ycentre - L,ycentre + L,N);0.13s, 0% 11: [X,Y] = meshgrid(x,y);0.67s, 2% 12: Z = X + i*Y;13 : Z0 = Z;14: for k = 1:50;23.02s, 76% 15: Z = Z.^2 + Z0;0.02s, 0% 16: end0.36s, 1% 17: ind1 = find(isnan(Z));0.43s, 1% 18: ind2 = find(~isnan(Z));0.22s, 1% 19: Z(ind1) = 1;0.08s, 0% 20: Z(ind2) = 0;5.15s, 17% 21: contour(x,y,abs(Z),[.5 .5])0.02s, 0% 22: grid;box23: axis equal offMost of the time here is spent iterating the values of Z. You can geta plot of the time taken by the most time-consuming lines of code bycapturing the output of the profile command and using it to produce apareto chart:>> t = profilet =file: [ 1x64 char ]interval: 0.0100count: [23x1 double]state: ’off’>> pareto(t.count)7733600040002000015 12 21100%78%52%26%0%Here only the three most time-consuming lines (labelled on the x axis)are shown, the rest taking too little time to be of concern. The left-handscale shows the time taken to do each line, in hundredths of a second.The line is the cumulative time. If we wanted to speed up this code, wewould do well to concentrate on line 15, and forget trying to speed upthe graphics.Profile in MATLAB 5.3The profile command has been significantly expanded in matlab 5.3.Use profile on to switch on the profiler. A hypertext report is producedby typing profile report. A graphical display of the profileresults is obtained by typing profile plot.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
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Where p i is the population for yea
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NaNs by leaving them off the plot.
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clfpolar(t,gdb)In this case you mus
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-0.5000-0.3750-0.2500-0.125000.1250
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the periodograms of the blocks, and
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plot(y(1:1000))axis([0 1000 -5 5])z
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comet(x,y)(You can get a three-dime
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By clicking within the panner box a
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x = linspace(-1,1,8192);Fs = 1000;y
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23.3 Graphical Object Hierarchymatl
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Now we need to get the handles of a
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Beyond the BasicsPreludeThis part o
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clfgplot(A,[x y])axis off(Try zoomi
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str =you’re the one>> str = ’
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strrep(str,’go’,’am’)ans =I
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ans =3.14159e+100Some additional te
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eval(str)v =1 2 3 4 5The eval(str)
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Inline objects, like every other ma
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a(1,1) = {[1 2 3]}a =[1x3double]or>
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t = {’help’ spiral(3) ; eye(2)
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meteo.Temperatureans =24ans =19.000
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3 >> a = [1 2 ;4 5 6;7 8 9]a =1 2 3
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[x,y] = meshgrid(1:5,1:3)x =1 2 3 4
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ans(:,:,2) =999And to sum over “p
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An Application of RGB ImagesTo see
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You can see that over the 8 time st
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name>> staff(2,1,2).name(5:9)ans =B
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q =7 8 96 1 25 4 3>> save saved_dat
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fid = fopen(’asc.dat’);The fope
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display and the enclosed area is th
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MarkerEdgeColor = auto(and so on)In
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text(-.7,f(-.7),’f(X)’)But we h
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plt(x,f(x/2),’--’)Let us try ca
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Example: findobjThe findobj command
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3. Add the property you want to set
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is numbered from top to bottom. The
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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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Page 145 and 146: 1. Use graphical elements that serv
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Page 149 and 150: uicontrol(’Pos’,[110 280 60 19]
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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
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Page 161 and 162: InvertHardcopy: [ {on} | off ]Paper
Page 163 and 164: Another option is to use an image f
Page 165 and 166: yur is the y coordinate of the uppe
Page 167 and 168: \end{center}\caption{This is the fi
Page 169 and 170: x 294x1 ...y 294x1 ...z 294x1 ...Gr
Page 171 and 172: diagram. Such a triangular grid can
Page 173 and 174: xt = x([1 9 10 1]);yt = y([1 9 10 1
Page 175 and 176: x = [0 0 .5 0.5 .5 1 11 .5 .5 .5];y
Page 177 and 178: fac2 = [1 2 61 6 31 4 61 6 5];The r
Page 179 and 180: t = linspace(0,2*pi,20);x = cos(t);
Page 181 and 182: N = 20;dt = 2*pi/N;t = 0:dt:(N-1)*d
Page 183 and 184: colouring of the sphere itself. To
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Page 191: 38.3 Debuggingmatlab has a suite of
Page 195 and 196: We change variables:p ′ = C + Bx.
Page 197 and 198: Exercise 6 (Page 59)You can generat
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Page 201 and 202: R = 1; N = 200;[x,y] = meshgrid(lin
Page 203 and 204: (The plot might take a few seconds
Page 205: % Reproduce the layers at the diffe
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