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weiqingchina

铜虫 (小有名气)

[求助] 一个复杂函数的matlab绘图

函数如下
z = 10681093296868640625*(-y^(500/161)*(24457*(4/25-x^2)^(1/2)*(1/25000)-24457/62500)/(238763*(201/500-(4/25-x^2)^(1/2))^(822/161)*(1/411000)+25921*((4/25-x^2)^(1/2)-201/500)^(822/161)*(1/411000)))^(161/500)*(1/268435456)
是一个关于xy的函数,绘图的程序如下
[x,y] = meshgrid(0:0.1:1);
z=(10681093296868640625*(-(y^(500/161)*((24457*(4/25 - x^2)^(1/2))/25000 - 24457/62500))/((238763*(201/500 - (4/25 - x^2)^(1/2))^(822/161))/411000 + (25921*((4/25 - x^2)^(1/2) - 201/500)^(822/161))/411000))^(161/500))/268435456;
mesh(x,y,z),xlabel('x'),ylabel('y'),zlabel('z')
报错如下
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 5.690563e-277.
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND =  1.869958e-36.
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND =  1.869958e-36.
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND =  7.144626e-19.
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND =  1.869958e-36.
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND =  7.144626e-19.
Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND =  1.847973e-34.
Error using  ^
Input to EIG must not contain NaN or Inf.
Error using mesh (line 76)
X, Y, Z, and C cannot be complex
有人能解决么
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weiqingchina

铜虫 (小有名气)

引用回帖:
3楼: Originally posted by dingd at 2013-04-09 08:43:53
公式中有“(4/25-x^2)^(1/2)”项,x范围为,会出现4/25-x^2<0的情况,此时开方只能得到复数。

要是不能画图,我就不画了吧
6楼2013-04-12 12:58:52
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jiji_n

木虫 (小有名气)

【答案】应助回帖

感谢参与,应助指数 +1
[x,y] = meshgrid(0:0.1:1, 0:0.1:1);
z=(10681093296868640625*(-(y.^(500/161).*((24457.*(4/25 - x.^2).^(1/2))/25000 - 24457/62500))./((238763*(201/500 - (4/25 - x.^2).^(1/2)).^(822/161))/411000 + (25921*((4/25 - x.^2).^(1/2) - 201/500).^(822/161))/411000)).^(161/500))/268435456;
figure,mesh(x,y,abs(z))
% 我也不知道为什么算出来是复数,你得仔细查查
2楼2013-04-09 08:05:46
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dingd

铁杆木虫 (职业作家)

【答案】应助回帖

感谢参与,应助指数 +1
公式中有“(4/25-x^2)^(1/2)”项,x范围为[0,1],会出现4/25-x^2<0的情况,此时开方只能得到复数。
3楼2013-04-09 08:43:53
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wangyuewu08

木虫 (著名写手)

这种情况,你应该把公式写成人容易读懂的形式贴上来,搞张图片,要不然看起来很费劲
往事并不如烟
4楼2013-04-09 17:16:13
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