应用MATLAB图形函数和绘图实例

1、应用MATLAB图形函数和绘图实例例1. 输入MATLAB程序如下：x = 0 : 0.2 : 12;y1 = Bessel ( 1, x );y2 = Bessel ( 2, x );y3 = Bessel ( 3, x );figure ( 1 )subplot ( 2, 2, 1 )h = plot ( x, y1, x, y2, x, y3 );set ( h, LineWidth, 2, LineStyle, - ; : , -. )set ( h, Color , R; G ; B )axis ( 0 12 0.5 1 )grid onxlabel ( Time )ylabel (

2、 Amplitude )legend ( h, First, Second , Third )title ( Bessel Functions) y, ix = min ( y1 );text ( x ( ix ), y, First Min rightarrow, HorizontalAlignment, right) Print depsc -tiff r200 myplot改变一个轴的3D视角按这些钮开始增加字符箭头和线按此按钮开始图形编辑模式应用图形编辑模式如图所示。同学们自己练习各项功能。例2. 输入MATLAB程序如下：t = 0 : pi/100 : 2*pi;y = sin (

3、 t );plot ( t, y )grid on继续输入程序如下：y2 = sin ( t 0.25 );y3 = sin ( t 0.5 );plot ( t, y, t, y2, t, y3 ) 可以对线的类型进行定义：t = 0 : pi/100 : 2*pi;y = sin ( t );y2 = sin ( t 0.25 );y3 = sin ( t 0.5 );plot ( t, y, - , t, y2, - , t, y3, : )练习，对红的颜色进行编辑。例3. 只绘数据点。输入MATLAB程序如下：x = 0 : pi / 15 : 4*pi;y = exp ( 2*cos

4、 ( x ) );plot ( x, y, r+ )进一步对图形进行设置：x = 0 : pi / 15 : 4*pi;y = exp ( 2*cos ( x ) );plot ( x, y, -r , x, y, ok )继续对线类型进行设置：x = 0 : pi / 15 : 4*pi;y1 = exp ( 2*cos ( x ) ); y2 = exp ( 2*sin ( x ) );plot ( x, y1, -*k , x, y2, -.ok )练习：把这两条曲线高成不同颜色。例4. 矩阵的线绘。z = peaks; %矩阵为4949plot ( z )变换方向来绘图：y = 1 :

5、 length ( peaks );plot ( peaks, y ) 例5. 用双Y轴绘曲线。t = 0 : pi/20 : 2*pi;y = exp ( sin ( t ) );plotyy ( t, y, t, y , plot, stem )把线性轴和对数轴合并绘图。t = 0 : 900; A = 1000; a = 0.005; b = 0.005;z1 = A * exp ( -a * t );z2 = sin ( b * t ); haxes, hline1, hline2 = plotyy ( t, z1, t, z2, semilogy, plot );axes ( hax

6、es ( 1 ) )ylabel ( Semilog Plot )axes ( haxes ( 2 ) )ylabel ( Linear Plot )set (hline2, LineStyle, - )例6. 轴的限制和标记。命令为： axis ( xmin, xmax, ymin, ymax )。专用标记和标记标号：x = -pi : .1 : pi;y = sin ( x );plot ( x, y )set ( gca, XTick, -pi : pi/2 : pi )set ( gca, XTickLabel, -pi, -pi/2, 0, pi/2, pi )xlabel ( -

7、pi leg Theta leg pi )ylabel ( sin ( Theta ) )title ( plot of sin ( Theta )text ( -pi/4, sin ( -pi/4 ), leftarrow sin (-pidiv4 ), HorizontalAlignment, left)set ( findobj ( gca, Type, line, Color, 0 0 1 , Color, 0.5 0 0.5 , Linewidth, 2 )例7. 绘椭圆。t = 0 : pi/20 : 2*pi;plot ( sin ( t ), 2*cos ( t ) )grid

8、 on当再加入命令axis square 后，绘出图形为如果所加入命令axis equal 后，绘出图形为如果所加入命令 axis equal tight 后，绘出图形为例8. 显示多个图形。t = 0 : pi/20 : 2*pi; x, y = meshgrid ( t );subplot ( 2, 2, 1 )plot ( sin ( t ), cos ( t ) )axis equalsubplot ( 2, 2, 2 )z = sin ( x ) + cos ( y );plot ( t, z )axis ( 0 2*pi -2 2 )subplot ( 2, 2, 3 )z = s

9、in ( x ).*cos ( y );plot ( t, z )axis ( 0 2*pi -1 1 )subplot ( 2, 2, 4 )z = ( sin ( x ).2 ) ( cos ( y ).2);plot ( t, z )axis ( 0 2*pi -1 1 )例9. 计算标注文字的位置。t = 0 : 900;hold on;plot ( t, 0.25 * exp ( -0.005 * t ) );text ( 300, .25 * exp ( -0.005 * 300 ), bullet leftarrow fontname times 0.25 ite -0.005

10、itt at t = 300 , FontSize , 14 )hold off;例10更详细标注信息。x = linspace ( 0, 2 * pi, 60 );a = sin ( x );b = cos ( x );hold onstem_handles = stem ( x, a + b );plot_handles = plot ( x, a, r, x, b, -g);xlabel (Time in musecs )ylabel (Magnitude )title (Linear Combination of Two Functions )legend_handles = stem

11、_handles ; plot_handles ;legend ( legend_handles, a + b, a = sin ( x ), b = cos ( x ) ) 例11. 更为复杂的标注说明，包括不同统计量。x = 0:.2:12; plot(x,bessel(1,x),x,bessel(2,x),x,bessel(3,x); legend(First,Second,Third); legend(First,Second,Third,-1) b = bar(rand(10,5),stacked); colormap(summer); hold on x = plot(1:10,5

12、*rand(10,1),marker,square,markersize,12,. markeredgecolor,y,markerfacecolor,.6 0 .6,. linestyle,-,color,r,linewidth,2); hold off legend(b,x,Carrots,Peas,Peppers,Green Beans,. Cucumbers,Eggplant) x = 0:.2:12; plot(x,bessel(1,x),x,bessel(2,x),x,bessel(3,x); legend(First,Second,Third); legend(First,Sec

13、ond,Third,-1) b = bar(rand(10,5),stacked); colormap(summer); hold on x = plot(1:10,5*rand(10,1),marker,square,markersize,12,. markeredgecolor,y,markerfacecolor,.6 0 .6,. linestyle,-,color,r,linewidth,2); hold off legend(b,x,Carrots,Peas,Peppers,Green Beans,. Cucumbers,Eggplant)离散数据图形例1. 二维的茎图。用函数。1）

14、 连续图形alpha = .02; beta = .5; t = 0 : 4 : 200y = exp ( -alpha*t ).*sin ( beta*t );plot ( t, y )2） 二维的茎图函数为stem ( t, y ), 个体具体如下：alpha = .02; beta = .5; t = 0 : 4 : 200;y = exp ( -alpha*t ).*sin ( beta*t );stem ( t, y )xlabel ( Time in musecs )ylabel ( Magnitude )把茎图和线图同时画在一个图上。请参考上一节中的例10.例2. 画一个3D F

15、FT 的茎图。th = ( 0: 127 ) / 128*2*pi;x = cos ( th );y = sin ( th );f = abs ( fft ( ones ( 10, 1 ), 128 ) );stem3 ( x, y, f , d, fill)view ( -65 30 )xlabel ( Real )ylabel ( Imaginary )zlabel ( Amplitude )title ( Magnitude Frequency Response )例3. 把茎图和线图同时画在一个图上。t = 0 : .1 : 10;s = 0.1 + i;y = exp ( -s*t

16、);stem3 ( real ( y ), imag ( y ), t, r )hold onplot3 (real ( y ), imag ( y ), t, r)hold offview ( -39.5, 62 ) xlabel ( Real )ylabel ( Imaginary )zlabel ( Amplitude )例4. 函数的阶梯绘图。alpha = 0.01;beta = 0.5;t = 0 : 10;f = exp ( - alpha*t ).* sin ( beta * t );stairs ( t, f )hold on plot ( t, f, -*)hold off

17、label = Stairstep plot of e-(alpha*t) sinbeta*t;text ( 0.5, -0.2, label , FontSize, 14 )xlabel ( t = 0 : 10, FontSize, 14 )axis ( 0 10 1.2 1.2)例5. 方向和速度矢量图。函数有compass, feather, quiver, quiver3。wdir = 45 90 90 45 360 335 360 270 335 270 335 335;knots = 6 6 8 6 3 9 6 8 9 10 14 12 ;rdir = wdir * pi / 1

18、80; x, y = pol2cart ( rdir , knots);compass ( x, y )desc = Wind Direction and Strength at , Logan Airport for , Nov . 3 at 1800 through , Nov. 4 at 0600 ;text ( -28, 15, desc )例6. 应用Feather 函数绘画。theta = 90 : -10 : 0; r = ones ( size ( theta ) ); u , v = pol2cart ( theta * pi / 180 , r * 10 );feather

19、 ( u , v )axis equal例7. 绘复数函数。t = 0:0.5: 10;s = 0.05 + i ;z = exp ( - s * t );feather ( z )例8. 二维的Quiver 函数绘画。n = -2.0 : .2 : 2.0 ; X , Y , Z = peaks ( n );contour ( X , Y , Z , 10 ) U , V = gradient ( Z , .2 );hold onquiver ( X , Y , U , V )hold off例9. 三维的Quiver 函数绘。vz = 10; a = -32; t = a: .1: 1;

20、z = vz * t + 1/2 * a * t . 2;vx = 2; x = vx * t; vy = 3; y = vy * t;u = gradient ( x ); v = gradient ( y ); w = gradient ( z );scale = 0;quiver3 ( x , y , z , u , v , w , scale )axis square例10. 创建一个简单的Contour函数绘图。 X , Y , Z = peaks;contour ( X , Y , Z , 20 )继续画3D图 X , Y , Z = peaks;contour3 ( X , Y

21、, Z , 20 )h = findobj ( Type , patch );grid offset ( h , LineWidth , 2 )title ( Twenty Contours of the peaks Function )例11. 在Contour绘制的图上标记数值。z = peaks ; C , h = contour ( z , 10 );clabel ( C , h )title ( Contour Labeled Using , clabel ( C , h ) )例12. 填充的Contour绘的图z = peaks ; C , h = contourf ( z ,

22、10 );caxis ( -20 20 )title ( Filled Contour Plot Using , Contourf ( z , 10 ) )例13. 以极坐标形式显示Contour函数绘图。 th , r = meshgrid ( ( 0 : 5 :360 ) * pi /180 , 0 : .05 :1 ); X , Y = pol2cart ( th , r ) ;Z = X + i * Y;f = ( Z . 4 1 ) . ( 1 / 4 );surf ( X , Y , abs ( f ) )hold onsurf ( X , Y , zeros ( size ( X

23、 ) ) )hold offxlabel ( Real )ylabel ( Imaginary )zlabel ( Abs ( f )例14. 在迪卡尔坐标系中的Contour图。 th , r = meshgrid ( ( 0 : 5 :360 ) * pi /180 , 0 : .05 :1 ); X , Y = pol2cart ( th , r ) ;Z = X + i * Y; f = ( Z . 4 1 ) . ( 1 / 4 );contour ( X , Y , abs ( f ) , 30 )axis ( -1 1 1 1 )xlabel ( Real , FontSize

24、, 14 )ylabel ( Imaginary , FontSize , 14 )例15. 在极轴坐标系中的Contour图。 th , r = meshgrid ( ( 0 : 5 :360 ) * pi /180 , 0 : .05 :1 ); X , Y = pol2cart ( th , r ) ;h = polar ( 0 2*pi , 0 1 )delete ( h )Z = X + i * Y; f = ( Z . 4 1 ) . ( 1 / 4 );hold oncontour ( X , Y , abs ( f ) , 30 )交互式绘图例1. 从屏幕上选择绘图的点。axi

25、s ( 0 10 0 10 )hold onxy = ;n = 0 ;disp ( Left mouse button picks points . )disp ( Right mouse button picks last points . )but = 1 ;while but = 1 xi , yi , but = ginput ( 1 ) ;plot ( xi , yi , ro )n= n + 1 ;xy ( : , n ) = xi ; yi ;endt = 1 : n ;ts = 1 : 0.1 :n ;xys = spline ( t , xy , ts );plot ( xys ( 1 ,: ) , xys ( 2 ,: ) , b-)hold off 例2. 创建和运行一个Movie，图象为最后结果。for k = 1 : 16 plot ( fft ( eye ( k + 16 ) ) )axis equalM ( k ) = getframe ;endmovie ( M , 30 )例3. 擦除模式动画。， 其中。A = -8/3 0 0 ; 0 10 10 ; 0 28 1 ;y = 35 10 7; 0 0 0; 0 0 0 ;h = 0.01;p = plot3 ( y ( 1