How to use ode45 with initial conditions defined in script?

Question

adi kul 2016-9-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/303421-how-to-use-ode45-with-initial-conditions-defined-in-script

回答： Steven Lord 2016-9-17

Hello, I am using ode45 to solve a differential equation. Here is the function file:

.m

function TempP=primary(Tp,y)
hp=13.64;
Tw=25;
mp=0.007;
Cp=1005;
TempP=-2*hp*(Tp-Tw)/(mp*Cp);

Now I have code in script: demo.m

clear all
yrange=[0:0.02:0.9];
Tp=40;
[Tp,y]=ode45(@primary,yrange,Tp);
figure(1)
plot(Tp,y)
ylabel('Tp (deg C)')
xlabel ('Y (m)')

If you can notice, the variables hp,Tw,mp,Cp are defined in primary.m but what I want is, to define in them in demo.m This will help me to control the initial conditions when I have such more function .m files. Is that possible?

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Answer 1

Star Strider 2016-9-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/303421-how-to-use-ode45-with-initial-conditions-defined-in-script#answer_235082

在 MATLAB Online 中打开

You can easily pass your parameters to ‘primary’ from ‘demo’:

function TempP=primary(Tp,y,hp,Tw,mp,Cp)
TempP=-2*hp*(Tp-Tw)/(mp*Cp);
end
hp=13.64;
Tw=25;
mp=0.007;
Cp=1005;
yrange=[0:0.02:0.9];
Tp0=40;
[Tp,y]=ode45(@(Tp,y) primary(Tp,y,hp,Tw,mp,Cp),yrange,Tp0);
figure(1)
plot(Tp,y)
ylabel('Tp (deg C)')
xlabel ('Y (m)')