integration with limits using an array

7 次查看（过去 30 天）
James Keiser
James Keiser 2022-10-6
评论： the cyclist 2022-10-6
I am trying to integrate an equation and it works when I do not have limits but when I add them it does not work.
u_wake is a 1x56 array, rho is a constant and 0.07 and 0.13 are the limit boundaries.
This works when I use this:
Drag = rho*trapz(u_wake.*(21.15-u_wake));
But not when I do this:
Drag = rho*trapz(u_wake.*(21.15-u_wake),0.07,0.13);
  3 个评论
显示 1更早的评论
James Keiser
James Keiser 2022-10-6
编辑：James Keiser 2022-10-6
I cannot upload the data because it is 56 files and I am only allowed to upload 10. The data is 56 numbers all below 21.15 .
The error code is:
Error in wake_scan_sample (line 35)
Drag = rho*trapz(u_wake.*(21.15-u_wake),0.07,0.13);
the cyclist
the cyclist 2022-10-6
It's unclear to me why you can't just upload u_wake, which is just a 1x56 vector.
Also, that is not the complete error message, which I am guessing looks something more like ...
Error using matlab.internal.math.getdimarg
Dimension argument must be a positive integer scalar within indexing range.
Error in trapz>getDimArg (line 90)
dim = matlab.internal.math.getdimarg(dim);
Error in trapz (line 36)
dim = min(ndims(y)+1, getDimArg(dim));
Error in wake_scan_sample (line 35)
Drag = rho*trapz(u_wake.*(21.15-u_wake),0.07,0.13);

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

the cyclist
the cyclist 2022-10-6
Looking at the documentation for trapz, it doesn't seem like the syntax you are trying to use is valid.
  2 个评论
the cyclist
the cyclist 2022-10-6
Ran in:
I assume that u_wake is the "y" value of the integral. Are 0.07 and 0.13 the endpoints of the "x" value? Are the values of u_wake at evenly spaced points along x? Then
Drag = rho*trapz(linspace(0.07,0.13,length(u_wake)),u_wake.*(21.15-u_wake));
should calculate what you want. For example,
% I just made up some u_wake and rho data
u_wake = sort(rand(1,56));
rho = 1;
Drag = rho*trapz(linspace(0.07,0.13,length(u_wake)),u_wake.*(21.15-u_wake))
Drag = 0.5618

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息

标签

产品


版本

R2022b

Community Treasure Hunt

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

Start Hunting!

Translated by