matlab學習2-畫線

一、二維曲線

1.1plot（x,y,線性）

在【0，2pi】畫sin(x),cos(x)的圖

x=linspace(0,2*pi,30);
plot(x,sin(x),'r',x,cos(x),'-')

1.2符號函數畫圖ezplot('f(x)',[a,b])

一、在【0，pi】上畫y=sin(x)

ezplot('sin(x)',[0,pi])

二、在【0，2pi】畫cos(t)^3,sin(t)^3,星圖

ezplot('cos(t)^3','sin(t)^3',[0,2*pi])

三、在[-2，0.5]，[0，2]上畫隱函數 exp(x)+sin(x*y）=0的圖

ezplot('exp(x)+sin(x*y)',[-2,0.5,0,2])

1.3flot('fun',lims)畫圖

fun是創建M文件或者是獨立變量的x的字符串

fplot('[tanh(x),sin(x),cos(x)]',2*pi*[-1,1,-1,1])

1.4對數座標圖

x=logspace(-1,2);
loglog(x,exp(x),'-s')
grid on

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二、三維圖像

2.1plot(x,y,z,線形)

t=0:pi/50:10*pi;
plot3(sin(t),cos(t),t)
rotate3d

x=-3:0.1:3;y=1:0.1:5;
[X,Y]=meshgrid(x,y);%爲了產生矩陣
Z=(X+Y).^2;
plot3(X,Y,Z)

2.2surf(x,y,z)畫出數據點（x,y,z）表示的曲面

x=-3:0.1:3;
y=1:0.1:5;
[X,Y]=meshgrid(x,y);
Z=(X+Y).^2;
surf(X,Y,Z)
shading  flat%將圖像變得平滑

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三、圖像處理

3.1加座標說明，表名，加格柵

3.2在圖像的線上標註名稱，gtext('名字')

x=linspace(0,2*pi,30);
 y=sin(x);
 z=cos(x);
 plot(x,y,x,z);
gtext('sin(x)');gtext('cos(x)')

3.3定製座標Axis([xmin,xmax,ymin,ymax,zmin,zmax])

x=linspace(0.0001,0.01,1000);
 y=sin(1./x);
 plot(x,y)
axis([0.005,0.01,-1,1])

3.4分割窗口subplot

x=linspace(0,2*pi,100);
 y=sin(x); z=cos(x);   
 a=sin(x).*cos(x);b=sin(x)./(cos(x)+eps)
 subplot(2,2,1);plot(x,y),title('sin(x)')
 subplot(2,2,2);plot(x,z),title('cos(x)')
 subplot(2,2,3);plot(x,a),title('sin(x)cos(x)')
 subplot(2,2,4);plot(x,b),title('sin(x)/cos(x)');

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特殊函數圖像

一、極座標圖polar (theta弧度,rho極半徑,s)

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theta=linspace(0,2*pi),                         
rho=sin(2*theta).*cos(2*theta);
polar(theta,rho,'g')
title('Polar plot of sin(2*theta).*cos(2*theta)');

二、散點圖、等值線平面圖

[X,Y]=meshgrid(-2:.2:2,-2:.2:3);
Z=X.*exp(-X.^2-Y.^2);
[C,h]=contour(X,Y,Z);
clabel(C,h)
colormap cool

山峯的三維和二維等值線圖。空間等值線圖： contour 3(x,y,z,n)，n爲等值線數

[x,y,z]=peaks;
        subplot(1,2,1)       
        contour3(x,y,z,16,'s')   
        grid,   xlabel('x-axis'),ylabel('y-axis')
        zlabel('z-axis')
        title('contour3 of peaks'); 
        subplot(1,2,2)
        contour(x,y,z,16,'s')
        grid,  xlabel('x-axis'), ylabel('y-axis')
        title('contour of peaks');