integrate function

5 次查看（过去 30 天）
kostas
kostas 2011-8-25
Hi!!!
I would like to ask if anyone knows what's the appropriate way to calculate the integral of this function
function out = Gr(u,x,Kt,i)
out= exp(-(u.^2)).*frustration_function2(u,x,Kt,i);
end
The integrating variable is u, and the limits are [1e-4,1e4]
Thanks!!

请先登录，再回答此问题。

回答（2 个）

Andrei Bobrov
Andrei Bobrov 2011-8-25
variant
x = ...;
Kt = ...;
i = ...;
quad(@(u)exp(-(u.^2)).*frustration_function2(u,x,Kt,i),
1e-4,1e4)
  7 个评论
显示 5更早的评论
Andrei Bobrov
Andrei Bobrov 2011-8-25
Hi Walter! Your last comment - the correct answer.
Bellow example, with use Maple Toolbox.
>> intd=@(Kt,i1)quad(@(x)exp(x).*arrayfun(@(X)quad(@(u)u+X+Kt+i1,0,1),x),0,1)
intd =
@(Kt,i1)quad(@(x)exp(x).*arrayfun(@(X)quad(@(u)u+X+Kt+i1,0,1),x),0,1)
>> intd(3,3)
ans =
12.169
>> syms Kt i1 x u
int(exp(x)*int(u+x+Kt+i1,u,0,1),x,0,1)
ans =
1/2 - Kt - i1 + 1/2 exp(1) + exp(1) Kt + exp(1) i1
>> double(subs(ans,[Kt,i1],[3,3]))
ans =
12.169
>>
Walter Roberson
Walter Roberson 2011-8-25
Ah good... it was around 4 AM when I wrote that, so I'm glad to see that I didn't do much worse than miss a "(" in the inner anonymous function!

请先登录，再进行评论。

kostas
kostas 2011-8-25
i mean that the result of the quad need to be scalar
  1 个评论
Walter Roberson
Walter Roberson 2011-8-25
The results of the quad cannot be scalar. My sentence "The function y = fun(x) should accept a vector argument x and return a vector result y, the integrand evaluated at each element of x." was a direct quote from the reference documentation for quad. quad does not just do one evaluation at a time: it selects a number of x and requests that the fun do the evaluation with respect to each of them and return the vector of corresponding answers.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Programming 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