using ode45 with input arrays

Question

Clarisa Williams 2012-6-27

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42215-using-ode45-with-input-arrays

I am trying to use ode45 but I have three arrays and can't get it to work.

Here is my function:

function [ ydot] = integration( t )
%This function will integrate 
theta=[2.05320782261561,2.05350842309907, etc. it is a 1x753 array gamma=[0.0919239472479973,0.0916551270720756,et. It is also a 1x753 array velocity=[157;165.432396880000;189.834767478843; etc. It is a 754x1 array 
y(1)= velocity*cos(gamma)*cos(theta)
y(2)= velocity*sin(gamma)*sin(theta)
y(3)= velocity*sin(gamma)
end

Here is my script program:

tspan=[0 753];
yo=[0.710174472636493,4.98858733451279, 0]
[t,y]=ode45(@integration, tspan,yo)
size(t)

I tried this for if theta, gamma, and velocity equal a single number and it worked but I cannot get it to work in the array. I copied and pasted the arrays from .mat files, which I was given to work with.

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Richard Brown 2012-6-28

编辑：Richard Brown 2012-6-28

Please format your code by selecting it and using the Code button.

(thanks Walter)

Jan 2012-6-28

What does "can't get it to work" explicitly mean? Do you get an error message? If so, which one? Does Matlab moan, that you want to reply "ydot" but define "y" only?

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Answer 1

Richard Brown 2012-6-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/42215-using-ode45-with-input-arrays#answer_51972

编辑：Richard Brown 2012-6-28

在 MATLAB Online 中打开

OK, I understand what you're asking now

First make sure theta, gamma, and velocity are column vectors of the same length, and assuming the samples have unit spacing. Then

y = cumtrapz([velocity .* cos(gamma) .* cos(theta), ...
              velocity .* sin(gamma) .* sin(theta), ...
              velocity .* sin(theta)])

should do the trick. ode45 is not required as there is no dependence on y in your rhs.