syntax error with using the ode45 function

1 回表示 (過去 30 日間)
Eliraz Nahum
Eliraz Nahum 2018 年 9 月 29 日
回答済み: Eliraz Nahum 2018 年 9 月 29 日
hello,
I can't understand what I am doing wrong. the main code I am attaching is calling an external called "function". I added the external function as an additional file.
I am adding the error message as a photo.
pleas help!
thanks!!!
clear all
close all
clc
global M_rand index
n_iter=10; %number of iterations
var=1.5/100; %variation around the nominal value
M_rand=zeros(9,n_iter);
random_variables=zeros(9,n_iter);%columns of t1 w0 w11 t2 w12 w21 w22 T1 T2
random_variables_nom=[32.2,2797.64,1222.18,138.2,944.187,180.03,45.35,12221.82,1801.75]; %t1 w0 w11 t2 w12 w21 w22 T1 T2
random_variables_range=zeros(9,2);%columns of t1 w0 w11 t2 w12 w21 w22 T1 T2, while the first column in min and the second is max
for range_counter=1:1:9
random_variables_range(range_counter,1)=random_variables_nom(range_counter)*(1-var);
random_variables_range(range_counter,2)=random_variables_nom(range_counter)*(1+var);
end
for rand_counter=1:1:9
temp(rand_counter,:)=random_variables_range(rand_counter,1)+(random_variables_range(rand_counter,2)-random_variables_range(rand_counter,1))*rand(1,n_iter);
end
M_rand=temp;
g=9.8;
GM=0.039; %in MKS
q0=[0;(6.3782448*(10^6));10.585;60.03];
t_delta=0.01
t_span=[0:t_delta:150];
t=0;
F=@(t,q) [q(2);(-GM*(q(1)/(((q(1)^2)+q(3)^2)^1.5)))+(g*Functions(t_iter))*(q(2)/(((q(2)^2)+(q(4)^2))^0.5));q(4);(-GM*(q(3)/(((q(1)^2)+q(3)^2)^1.5)))+(g*Functions(t_iter))*(q(4)/(((q(2)^2)+(q(4)^2))^0.5))];
for counter_iter=1:1:n_iter
index=counter_iter;
for time=1:t_delta:length(t_span)
t_iter=time;
[t,q]=ode45(@(t,q) F(t,q),t_span,q0);
plot(t,q(1,:),'g')
hold on
plot(t,q(1,:),'g')
end
figure
end

採用された回答

Walter Roberson
Walter Roberson 2018 年 9 月 29 日
You define
F=@(t,q) [q(2);(-GM*(q(1)/(((q(1)^2)+q(3)^2)^1.5)))+(g*Functions(t_iter))*(q(2)/(((q(2)^2)+(q(4)^2))^0.5));q(4);(-GM*(q(3)/(((q(1)^2)+q(3)^2)^1.5)))+(g*Functions(t_iter))*(q(4)/(((q(2)^2)+(q(4)^2))^0.5))];
at a time when you have not yet defined t_iter . To use the current value of t_iter you need to move the definition of F to inside your for loop.
Your graphics are wrong. You have
plot(t,q(1,:),'g')
hold on
plot(t,q(1,:),'g')
but q is a 2D array with the same number of rows that t has, with one column per output variable. Perhaps you want plot(t, q(:,1), 'g') . But why do you plot the same thing again?
You also have this plot inside a for loop, causing it to plot each time. But your output is nearly the same each time, so you cannot tell the difference between the lines.
You are looping over t_span but each time calling ode45 for the entire t_span . Why are you doing that? Are you working on a system that has two time dimensions, both of which just happen to be the same size?

その他の回答 (1 件)

Eliraz Nahum
Eliraz Nahum 2018 年 9 月 29 日
first of all, thank you for replying. by the way, I am trying to learn Matlab by myself and not an experienced user of it.
so first of all let's give you a link to my original problem (not answered yet) so it may clarify what my final intention is.here is a link: my original problem
I guess that my problem is the fact that I am calling to an external time dependent function while performing the ODE45 one. so that's why I am trying to create a variable called t_iter, so my external function will get the relevant time.
as for the plot - you are right, there is a mistake. I should write plot(q(:,1),q(:,3),'g') for seeing Y vs X.
please help, I am lost.

カテゴリ

Help Center および File ExchangeBartlett についてさらに検索

製品


リリース

R2018a

Community Treasure Hunt

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

Start Hunting!

Translated by