关于绘制隐函数图形

悠若谷

在学习画隐函数图形的时候看到论坛的FAQ集里边有这样的问答
Q:如何在Matlab中画隐函数曲线？

A: 在http://www.mathworks.com/matlabcentral/fileexchange/index.jsp
        查找implicit，会找到一个Arthur Jutan写的implot.m


上面这个网站我打不开，显示
The page you were looking for doesn't exist.You may have mistyped the address or the page may have moved.

不知道哪位有implot.m原代码？能贴上来吗？

friendchj

Description
A basic plotting function for implicit functions of exactly two variables.  
Plots in the same way as implot.m (by Arthur Jutan), but extends the capabilities of implot.m to allow specification of one or more contourgroup properties: e.g. line width, line color, line style etc.

1. 
   
2. function [lineHandle, lineData] = implot2(varargin)
   
3. % IMPLOT2: Plots implicit functions.
   
4. %
   
5. % [H,DATA] = IMPLOT2(F,RANGE,N) plots an implicit function of exactly 2
   
6. % variables (e.g 'x' and 'y', but any variables will work).
   
7. % * F is a MATLAB inline function defined in form F(x,y)=0
   
8. % * RANGE = [xmin xmax ymin ymax] is the range over which F is plotted
   
9. % * N is no. of grid-points, per variable, in the discretisation used
   
10. % to calculate the plot ==> total no. grid-points ~ N^2
    
11. % * H is a handle to the plotted lineseries object; lineData is a
    
12. % two-row matrix containing the plotted x and y data. Each contiguous
    
13. % line segment is demarcated by a pair of NaN values.
    
14. %
    
15. % IMPLOT2(F), IMPLOT2(F,RANGE) plots as above, but using the default
    
16. % values {RANGE}=[-2*pi,2*pi,-2*pi,2*pi] and {N}=100 (as applicable)
    
17. %
    
18. % IMPLOT2(...,S,'PropertyName1',PropertyValue1,...) plots as above, but
    
19. % with parameter/value pairs specifying additional line properties, as
    
20. % per syntax in PLOT.m. Type DOC LINESERIESPROPERTIES for more info.
    
21. % S is an optional 1,2 or 3-element character string specifying line
    
22. % color, marker and/or style, also as per PLOT.m syntax.
    
23. %
    
24. % Example -- plot [2*sin(y)=x], [x^2+y^2=4], [sin(x)*cos(y)=pi/30]:
    
25. %
    
26. % f=inline('2*sin(y)-x','x','y'); g=inline('x^2+y^2-4','x','y');
    
27. % h=inline('sin(x)*cos(y)-pi/30','x','y');
    
28. % rangexy = [-2 2 -2 2]; hold on;
    
29. % implot2(f,'LineWidth',2,'Color',[0 0 1]);
    
30. % implot2(g,rangexy,200,'g-','LineWidth',2);
    
31. % [h,data] = implot2(h,'r:'); axis equal;
    
32. %
    
33. % --- AUTHOR: Vinesh Rajpaul (UCT)
    
34. % --- VERSION: 16 May 2009
    
35. %
    
36. % See also INLINE, PLOT, CONTOUR, CONTOURC
    
37. 
    
38. %% Specify default parameters
    
39. ngrid=100; % default: 100*100 gridpoints
    
40. rangexy=[-2*pi,2*pi,-2*pi,2*pi]; % default [x,y] range
    
41. lineSpec ='k-'; % default linestyle
    
42. 
    
43. %% Check number of input arguments; extract contourgroup properties
    
44. 
    
45. for i=1:nargin
    
46. if ischar(varargin{i})
    
47. propertyIndex = i; % index of first line property
    
48. break
    
49. end
    
50. end
    
51. 
    
52. if exist('propertyIndex','var')
    
53. properties = varargin(propertyIndex:nargin);
    
54. if mod(length(properties),2)~=0
    
55. lineSpec = properties{1}; % treat character string S separately
    
56. properties(1)=[];
    
57. end
    
58. nargs = propertyIndex-1;
    
59. else nargs = nargin;
    
60. end
    
61. 
    
62. if nargs < 1 || nargs >3
    
63. error('MATLAB:implot:InvalidInput', ...
    
64. '1 to 3 plotting arguments required. Type HELP IMPLOT2.')
    
65. end
    
66. 
    
67. switch nargs
    
68. case 1; % only an inline function specified
    
69. fun = varargin{1};
    
70. case 2; % as for nargin==1, with range also specified
    
71. [fun,rangexy] = deal(varargin{1:nargs});
    
72. otherwise % as for nargin==2, with gridpoints also specified
    
73. [fun,rangexy,ngrid]=deal(varargin{1:nargs});
    
74. end
    
75. 
    
76. %% Set up mesh grid; do plotting
    
77. 
    
78. xGrid=linspace(rangexy(1),rangexy(2),ngrid);
    
79. yGrid=linspace(rangexy(3),rangexy(4),ngrid);
    
80. [x,y]=meshgrid(xGrid,yGrid);
    
81. 
    
82. fvector=vectorize(fun); % vectorize the inline function
    
83. fvalues=feval(fvector,x,y);
    
84. cMatrix = contourc(xGrid,yGrid,fvalues,[0,0]);
    
85. 
    
86. variables = symvar(fun); % extract variables from inline function
    
87. 
    
88. lineData = separateLines(cMatrix); % separate contiguous lines
    
89. lineHandle = plot(lineData(1,:),lineData(2,:),lineSpec);
    
90. xlabel(variables(1)); ylabel(variables(2)); box on;
    
91. 
    
92. if exist('properties','var') % apply all specified line properties
    
93. nProps = length(properties);
    
94. set(lineHandle,properties(1:2:nProps),properties(2:2:nProps));
    
95. end
    
96. 
    
97. end
    
98. 
    
99. %% Demarcate contiguous line segments by NaN tokens
    
100. % (Mainly to facilitate plotting of noncontiguous segments via PLOT.m)
     
101. 
     
102. function lineData = separateLines(cMatrix)
     
103. lineData = cMatrix;
     
104. index = 1; % index of line segment demarcation
     
105. while index<length(lineData)
     
106. numPoints = round(lineData(2,index)); % no. datapoints in line
     
107. lineData(:,index)= NaN; % demarcate each contiguous line by NaN
     
108. index = index + numPoints +1; % advance to next token
     
109. end
     
110. end
     

复制代码

悠若谷

谢谢楼上的O(∩_∩)O~代码已经用上了！

[ 本帖最后由 悠若谷 于 2009-6-17 11:21 编辑 ]