清空筛选条件
清空筛选条件

how to calculate a derivative

508 次查看（过去 30 天）
Nasir Qazi
Nasir Qazi 2012-2-26
评论： Sergio E. Obando 2024-6-15
can some one guide me how to calculate a derivative and integration in matlab . can you please give a little example.

请先登录，再回答此问题。

采纳的回答

bym
bym 2012-2-26
Symbolically
syms x real
f = 1/x
int(f,1,2) % integration
ans =
log(2)
diff(f) %differentiation
ans =
-1/x^2
[edit - amplification]
syms x a b real positive
f = 1/x
f =
1/x
int(f) % without limits
ans =
log(x)
int(f,a,b) % with limits
ans =
log(b) - log(a)
fn = matlabFunction(f) % convert symbolic to anonymous function
fn =
@(x)1./x
quadgk(fn,1,2) % integrate numerically
ans =
0.6931
log(2) % previous result from symbolic integration
ans =
0.6931
(fn(2+1e-6)-fn(2))/1e-6 %numerical derivative at fn(2)
ans =
-0.2500
subs(diff(f),2) %substitute 2 into symbolic result previously obtained
ans =
-0.2500
  5 个评论
显示 3更早的评论
Jan
Jan 2012-2-27
Yes, Nasir, then the integral is calculated from 1 to 2. "Symbolically" mean calculations with symbols, usually characters. The result is a formula. "Numerically" means, that you calculate a numerical value, a number.
Sergio E. Obando
Sergio E. Obando 2024-6-15
Just here to suggest some recent resources, There is a nice section in the Symbolic Math Toolbox with additional examples for differentiation as well as a FEX curriculum on this topic:

请先登录，再进行评论。

更多回答（3 个）

Magdalena Glinska
Magdalena Glinska 2020-11-16
f = @(x) sin(x);
second_derivative_f = matlabFunction(diff(sym(f)));
Hamza saeed khan
Hamza saeed khan 2020-11-24
syms x
f = x;
diff(f,x)
why this code give me error as;
>>Error in diff (line 1)
syms x
  2 个评论
Walter Roberson
Walter Roberson 2020-12-22
You probably do not have the symbolic toolbox installed or licensed.
Also, you accidentally named your script diff.m which is going to conflict with calling diff() to differentiate.

请先登录，再进行评论。

Achimsettythanmay
Achimsettythanmay 2022-11-14
编辑：Walter Roberson 2022-11-15
Ran in:
syms x real
f = 1/x
f = 
int(f,1,2) % integration
ans = 
diff(f) %differentiation
ans = 

类别

在 Help Center 和 File Exchange 中查找有关 Special Values 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by