Help me about sphere ?

2014 5 27
1 个回答
更新时间：2014 5 27
6 次查看（30 天）

0 个投票

I have this code to draw haft of sphere x^2 + y^2 + z^2 = 1, z>0. but it have error. help me to fix it. thanks very much.

请先登录，再回答此问题。

回答（1 个）

Mischa Kim
Mischa Kim 2014-5-27
编辑：Mischa Kim 2014-5-27

1 个投票

Nguyen, use instead
z = real(sqrt(1 - x.^2 - y.^2));
to retain the real part only.

3 个评论
显示 1更早的评论 隐藏 1更早的评论

Nguyen Trong Nhan
Nguyen Trong Nhan 2014-5-27
编辑：Nguyen Trong Nhan 2014-5-27
oh thank. but why I have to use real(). these are positive numbers so the square root of them are also the real number, why does it appear complex number here ?
Mischa Kim
Mischa Kim 2014-5-27
编辑：Mischa Kim 2014-5-27
In a perfect world, yes. However, in numerical computations zero is not always (exactly) equal to zero. Check out this answer for reference. If you remove the semi-colon from
z = sqrt(1 - x.^2 - y.^2)
you'll notice that there are small non-zero imaginary parts.
Nguyen Trong Nhan
Nguyen Trong Nhan 2014-5-27
ah Mischa Kim, could you explain me when I need to use the eval and double funtions in matlab ?

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 App Building 的更多信息

产品

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by