Double numerical integration of an Experimental data (no function)

2016 8 10
1 个回答
更新时间：2016 8 10
28 次查看（30 天）

0 个投票

Hi all,
I have a rectangular domain ( in x and y) and have 64 points equally distributed data points around this rectangular domain (lets call the data points as A). I have the numerical value of each point on the grid. (sizes: x = 1 x 64, y = 1 x 64, A = 8 x 8)
B = double_integration(A) dx dy.
I tried the already given solution , result = trapz(x,trapz(y,mat,1),2) , but did not get any result. (Error was, LENGTH(X) must equal the length of Y in dim 1.)
Any ideas?
Many thanks

2 个评论
显示 无 隐藏 无

John D'Errico
John D'Errico 2016-8-10
Are the points scattered irregularly around the domain? Or are they on a regular lattice of some sort? Like an 8x8 grid?
Baris Gungordu
Baris Gungordu 2016-8-10
Yes the data points are arranged as 8 x 8 and I have coordinates in x and y for each point.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Star Strider
Star Strider 2016-8-10

0 个投票

I would use trapz on each dimension of ‘A’:
int_1 = trapz(A);
Result = trapz(int_1)

5 个评论
显示 3更早的评论 隐藏 3更早的评论

Baris Gungordu
Baris Gungordu 2016-8-10
编辑：Baris Gungordu 2016-8-10
I tried this, it worked but the result does not look right.
A = reshape(A,64,1);
for i = 1:64
int1(i,1) = trapz(Y64,A);
end
int2 = trapz(X64,int1);
Star Strider
Star Strider 2016-8-10
I thought ‘A’ is (8x8), and you want to integrate it.
The trapz function integrates a matrix by integrating the columns, creating a vector. The second trapz call integrates the vector to produce the result of the double integration.
What are your data and what do you want to do with them?
John D'Errico
John D'Errico 2016-8-10
Think of trapz as a single integration, along one axis of the array. You wanted to do a double integration. The first call to trapz will turn the array into a vector of length 8, integrating down the columns of your array by default. Then the second call will integrate the vector, so doing the outer integral.
Baris Gungordu
Baris Gungordu 2016-8-10
My data is 8x8 but I changed it to 64x1 to make the trapz work.
I want to double integrate my data first respect to x and then with respect to y.
Star Strider
Star Strider 2016-8-10
The trapz function works very well with matrices. It considers each column of a matrix as individual vectors, and integrates them, creating a vector. The second trapz call integrates the vector. I do not know what ‘x’ and ‘y’ are with respect to ‘A’, but you can easily transpose ‘A’ to integrate with respect to each variable in order, if necessary.

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Numerical Integration and Differentiation 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