FIND AREA SURFACE-PROBLEM IN MY CODE

Question

justin Taylor 2011-12-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/24736-find-area-surface-problem-in-my-code

syms u v;
x = (1-u).*(3+cos(v)).*cos(pi*u);
y = (1-u).*(3+cos(v)).*sin(pi*u);
z = 8*u+( 1-u ).*sin(v);
% Find Area Surface
F=[x,y,z];
F=[x,y,z];
ru=diff(F,u);
rv=diff(F,v);
ruxrv=[ru(2).*rv(3)-ru(3).*rv(2),ru(3).*rv(1)-ru(1).*rv(3),ru(1).*rv(2)-ru(2).*rv(1)];
Mruxrv=sqrt(ruxrv(1).^2+ruxrv(2).^2+ruxrv(3).^2)
Aresurface=quad2d(Mruxrv,0,1,0,2*pi)

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Answer 1

bym 2011-12-26

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/24736-find-area-surface-problem-in-my-code#answer_32498

在 MATLAB Online 中打开

the function is called

dblquad()

and requires a function to be passed to it like:

f = matlabFunction(Mruxrv);
Aresurface=dblquad(f,0,1,0,2*pi)
Aresurface =
     27.5280

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Walter Roberson 2011-12-26

quad2d is also a function to consider.

http://www.mathworks.com/help/techdoc/ref/quad2d.html

dblquad() offers a choice of quadrature methods, and expects that the function be vectorized in x and scalar in y

quad2d() does not offer flexibility. It expects that the function accepts 2D arrays for x and y.

For both integrators, there is a potential vulnerability in the matter of whether matlabFunction returns a vectorized function or not. It is documented that if matlabFunction is used to write to a file, that the file it produces will be optimized code that can accept scalar or matrix arguments, but it is not made explicit as to what arguments are accepted if writing to a file is not done, and it is not made explicit that the matrix arguments will be processed element-wise.

justin Taylor 2011-12-26