如何在Matlab的for循环中自动计算导数？
如何在Matlab的for循环中自动计算导数？
提问于 2020-04-30 22:08:35
为了推广的目的，我希望Matlab能自动计算相关函数f(x)的一阶和二阶导数。(如果我将f(x) = sin(6x)改为f(x) = sin(8x))
我知道有名为diff()和syms的内置命令，但我不知道如何在i循环中处理它们。这是我正在努力解决的关键问题。
如何对以下代码集进行更改？我正在使用MATLAB R2019b。
n = 10;
h = (2.0 * pi) / (n - 1);
for i = 1 : n
x(i) = 0.0 + (i - 1) * h;
f(i) = sin(6 * x(i));
dfe(i) = 6 * cos(6 * x(i)); % first derivative
ddfe(i) = -36 * sin(6 * x(i)); % second derivative
end回答 1
Stack Overflow用户
回答已采纳
发布于 2020-04-30 22:45:28
您可以简单地使用subs和double来完成此操作。对于您的案例：
% x is given here
n = 10;
h = (2.0 * pi) / (n - 1);
syms 'y';
g = sin(6 * y);
for i = 1 : n
x(i) = 0.0 + (i - 1) * h;
f(i) = double(subs(g,y,x(i)));
dfe(i) = double(subs(diff(g),y,x(i))); % first derivative
ddfe(i) = double(subs(diff(g,2),y,x(i))); % second derivative
end通过@Daivd注释，您还可以向量化循环：
% x is given here
n = 10;
h = (2.0 * pi) / (n - 1);
syms 'y';
g = sin(6 * y);
x = 0.0 + ((1:n) - 1) * h;
f = double(subs(g,y,x));
dfe = double(subs(diff(g),y,x)); % first derivative
ddfe = double(subs(diff(g,2),y,x)); % second derivative 页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/61525324
复制相关文章
相似问题
腾讯云开发者
