求助：隐函数画图问题

ssffss

形如
(x^2-y^2th(0.2y))tan(0.4x)-xy(1+th(0.2y))=0
的式子用 ezplot画出来的曲线为什么是杂乱的好多条呢?
怎么才可以画成一条呢?

qiuqia17

ding ~~

ssffss

请各位高手帮帮忙,急用

yqchenlolo

以前有人编的
function implot(fun,rangexy,ngrid)
% Implicit plot function
% function implot(fun,rangexy,ngrid)
% fun is 'inline' function f(x,y)=0 (Note function written as equal to zero)
% rangexy =[xmin,xmax,ymin,ymax] range over which x and y is ploted default(-2*pi,2*pi)
% ngrid is the number of grid points used to calculate the plot,
% Start with course grid (ngrid =20) and then use finer grid if necessary
% default ngrid=50
%
% Example
% Plot y^3+exp(y)-tanh(x)=0
%
% write function f as an 'inline' function of x and y-- right hand side equal to zero
%
% f=inline('y^3+exp(y)-tanh(x)','x','y')% implot(f,[-3 3 -2 1])
% A.Jutan UWO 2-2-98 ajutan@julian.uwo.ca
if nargin == 1 ;% grid value and ranges not specified calculate default
rangexy=[-2*pi,2*pi,-2*pi,2*pi];
ngrid=50;
end
if nargin == 2; % grid value not specified
ngrid=50;
end% get 2-D grid for x and y
xm=linspace(rangexy(1),rangexy(2),ngrid);
ym=linspace(rangexy(3),rangexy(4),ngrid);
[x,y]=meshgrid(xm,ym);
fvector=vectorize(fun);% vectorize the inline function to handle vectors of x y
fvalues=feval(fvector,x,y); %calculate with feval-this works if fvector is an m file too
%fvalues=fvector(x,y); % can also calculate directly from the vectorized inline function
contour(x,y,fvalues,[0,0],'b-');
% plot single contour at f(x,y)=0, blue lines
xlabel('x');
ylabel('y');
grid

chaoshui20

告诉你你区间没选对，因为你画的很可能是多值的

yqchenlolo

比如？举个例看看
这个也不是我写的，没怎么仔细去看

realyyy

如果区间设置为：rangexy=[-2*pi,2*pi,-2*pi,2*pi]，则图形1如下：

如果区间设置为：rangexy=[0,5,0,4.5]，则图形2如下：

toes

微微

好像在那个版有类似的帖子，楼主搜一下