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1、MATLAB (CH6)Additional Data Dypes and Plot Types2MATLAB (CH6) Complex data String functions Multidimensional arrays Additional data types 2D 3D Plots36.1.1 Complex Variablesc = a + bi = z a = zcos b = zsin 46.1.1 Complex Variables c=3+4ic = 3.0000 + 4.0000i c=3+4jc = 3.0000 + 4.0000i isreal(c)ans =
2、0 isreal(c)ans = 156.1.1 Complex Variables c=2 3;4 5c = 2 3 4 5 isreal(c)ans = 1 c=2 3;4 5ic = 2.0000 3.0000 4.0000 0 + 5.0000i isreal(c)ans = 066.1.2 Using Complex Numbers with Relational Operatorsn , = , c1=4+i*3; c2=3+i*8; c1c2 ans = 176.1.2 Using Complex Numbers with Relational Operatorsn= , =Bo
3、th the real parts and the imaginary parts are compared. c1=4+i*3; c2=4+i*8; c1=c2 ans = 086.1.3 Complex Functionsn conj(c) a-bi n real(c) an imag(c) bn isreal(c) n isreal(c) n abs(c) zn angle(c) (radian)c = a + bi = z 9Example(Quadratic Equation)% Calc_roots_2.mdisp(This program solves for the roots
4、 of a quadratic);disp(Equation of the form A*x2+B*X+C=0.);a=input(Enter the coefficient A: );b=input(Enter the coefficient B: );c=input(Enter the coefficient C: );10discriminant=b2-4*a*c;x1=(-b+sqrt(discriminant)/(2*a);x2=(-b-sqrt(discriminant)/(2*a);disp(The roots of this equation are:);fprintf(x1=
5、(%f)+i(%f)n,real(x1),imag(x1);fprintf(x2=(%f)+i(%f)n,real(x2),imag(x2);Example(Quadratic Equation)11 Calc_roots_2This program solves for the roots of a quadraticEquation of the form A*x2+B*X+C=0.Enter the coefficient A: 1Enter the coefficient B: 2Enter the coefficient C: 5The roots of this equation
6、are:x1=(-1.000000)+i(2.000000)x2=(-1.000000)+i(-2.000000)Example(Quadratic Equation)126.1.4 Plotting Complex DataPlot the functiont = 0:pi/20:4*piy = exp(-0.2*t).*(cos(t) + sin(t)if plot(t, y) is used, only the real data will be plotted!We should use:1. plot(t, real(y); or 2. plot(y); hold on; or 3.
7、 polar(angle(y),abs(y); plot (t, imag(y);136.1.4 Plotting Complex Datat=0:pi/20:4*pi;y=exp(-0.2*t).*(cos(t)+i*sin(t);plot(t,y,b-, LineWidth,5.0);title(bfplot of Complex Function vs Time);xlabel(bfitt);ylabel(bfity(t);grid on;14plot(t, y) Only the real data is shown.156.1.4 Plotting Complex Datat=0:p
8、i/20:4*pi;y=exp(-0.2*t).*(cos(t)+i*sin(t);plot(t,real(y),b-, LineWidth,5.0);hold on;plot(t,imag(y),r-, LineWidth,5.0);title(bfplot of Complex Function vs Time);xlabel(bfitt);ylabel(bfity(t);legend(real part, imaginary part)grid on;16plot(t, real(y); hold on; plot (t, imag(y);176.1.4 Plotting Complex
9、 Datat=0:pi/20:10*pi;y=exp(-0.2*t).*(cos(t)+i*sin(t);plot(y,b-,LineWidth,5.0);%(It is equal to plot(real(y), imag(y).title(bfPlot of Complex Function );xlabel(bfReal Part);ylabel(bfImaginary Part);axis equalgrid on;18plot(y)196.1.4 Plotting Complex Datat=0:pi/20:10*pi;y=exp(-0.2*t).*(cos(t)+i*sin(t)
10、;polar(angle(y),abs(y);title(bfPlot of Complex Function);20polar(angle(y),abs(y)216.2 String Functionse.g. str=Today is Sundaystr =Today is Sunday whos Name Size Bytes Class str 1x15 30 char arrayGrand total is 15 elements using 30 bytes Each character is stored in two bytes of memory.226.2.1 String
11、 Conversion Functions x=double(str)x = Columns 1 through 10 84 111 100 97 121 32 105 115 32 83 Columns 11 through 15 117 110 100 97 121 str2=char(x+5)str2 =Ytif%nx%Xzsif str3=char(double(str2)-5)str3 =Today is Sunday236.2.2 Creating Two-Dimensional Character Arrayse.g. MyUnv=QingDao;University? Erro
12、r using = vertcatAll rows in the bracketed expression must have the same number of columns. MyUnv=char(QingDao,University)MyUnv =QingDao University246.2.3 Concatenating StringsnFunction strcat concatenates two or more strings horizontally (delete trailing blanks)nFunction strvcat concatenates two or
13、 more strings vertically e.g. strcat(Red, Green ) ans = RedGreen strvcat(Hello,World) ans = Hello World256.2.4 Comparing Strings 6.2.4.1 Comparing Strings for Equalityn strcmp Determines if two strings are identical; n strcmpi Determines if two strings are identical ignoring case; n strncmp Determin
14、es if the first n characters of two strings are identical; n strncmpi Determines if the first n characters of two strings are identical ignoring case; 266.2.4 Comparing Strings 6.2.4.1 Comparing Strings for Equality276.2.4.2 Comparing Individual Characters for Equality and Inequalitye.g. a=QingDaoa
15、= QingDao b=huangdaob =huangdao a=b? Error using = eqMatrix dimensions must agree. 286.2.4.2 Comparing Individual Characters for Equality and Inequalitye.g. a= QingDao % pad with a blanka = QingDao b=huangdaob =huangdao a=bans = 0 0 0 1 1 0 1 1,=, str= hello, worldstr = hello, world isletter(str)ans
16、 = Columns 1 through 13 0 1 1 1 1 1 0 0 1 1 1 1 1 isspace(str)ans = Columns 1 through 13 1 0 0 0 0 0 0 1 0 0 0 0 0 306.2.6.5 Number to Stringnstr = num2str(number)nstr = sprintf(format, number) str = num2str(pi)str =3.1416 str = sprintf(The value of pi is %8.6f.,pi)str =The value of pi is 3.141593.
17、316.2.6.6 String to Number nvalue = str2double(str)nvalue = sscanf(str, format)e.g.a = 3.1415926 str2double(a)ans = 3.1416value1 = sscanf(a,%g)value1 = 3.1416value2 = sscanf(a,%d)value2 = 3 32Other String Functionsn findstrn strmatchn strrepn strtokn uppern lowern int2strn num2strn dec2hexn mat2strn
18、 sprintfn sscanf33Other String Functions346.3 Multidimensional Arrays356.3 Multidimensional Arrays c = randn(2,2,3)c(:,:,1) = 0.53767 -2.2588 1.8339 0.86217c(:,:,2) = 0.31877 -0.43359 -1.3077 0.34262c(:,:,3) = 3.5784 -1.3499 2.7694 3.0349 ndims(c)ans = 3 size(c)ans = 2 2 3366.4 Additional 2-D Plotsx
19、=1 2 3 4 5 6;y=2 6 8 7 8 5;stem(x,y);title(bfExample of a Stem Plot);xlabel(bfitx);ylabel(bfity);axis(0 7 0 10);37Additional 2-D Plots38Additional 2-D Plotsn bar(x,y)n barth(x,y)n compass(x,y)n pie(x)n pie(x,explode)n stairs(x,y)n stem(x,y)39Additional 2-D Plots40fplotCreate a file, myfun, that retu
20、rns a two-column matrix:function Y = myfun(x) Y(:,1) = 200*sin(x(:)./x(:); Y(:,2) = x(:).2;Create a function handle pointing to myfun:fh = myfun;Plot the function with the statementfplot(fh,-20 20) 41fplot426.5 3-D Plotst=(0:0.02:2)*pi;x=sin(t);y=cos(t);z=cos(2*t);plot3(x, y, z, b-);43plot3446.5 3-D
21、 Plots meshx,y=meshgrid(-4:0.2:4,-4:0.2:4); z=exp(-0.5*(x.2+0.5*y.2); mesh(x,y,z) xlabel(bfx); ylabel(bfy); zlabel(bfz);Use meshgrid to generate a legal 2D dot array before plotting a 3D plot.45mesh46surfx,y=meshgrid(-4:0.2:4,-4:0.2:4); z=exp(-0.5*(x.2+0.5*(x- y).2); surf(x,y,z) xlabel(bfx); ylabel(bfy); zlabel(bfz);47surf48x,y=meshgrid(-4:0.2:4,-4:0.2:4); z=exp(-0.5*(x.2+0.5*(x-y).2); contour(x,y,z) xlabel(bfx); ylabel(bfy); zlabel(bfz);contour49contour
