ode with varying constant

Question

prajyot gajbhiye 2020-10-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/621633-ode-with-varying-constant

回答： Star Strider 2020-10-21

i have one differntial eqation and in that i have two constants one is scalar and one is vector i have to solve diffential equation for each value of vector means i got no of diff equation= no of elements in vector now i have to plot each solution of each de with time

function [dydt] = diffvar(t,y)

dydt=-k*y+a;

end

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prajyot gajbhiye 2020-10-21

but you have considered both as scalar

Ameer Hamza 2020-10-21

That code will work even if you put one of the variable as scalar.

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Answer 1

Star Strider 2020-10-21

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/621633-ode-with-varying-constant#answer_520603

Interpolating a time-domain vector in a differential equation is essentially described in the ode45 (and other solvers) documentation. This simply re-states it in the context of the current problem.

Try this

ic = 0;
tspan = [0 10];
k = 42;
av = rand(1,10);                                                        % Vector Defining ‘a’
a = @(t) interp1(linspace(min(tspan),max(tspan),numel(av)), av, t);     % Function Interpolating ‘a’
[T,Y] = ode45(@(t,y)diffvar(t,y,k), tspan, ic);
figure
plot(T, Y)
grid
function [dydt] = diffvar(t,y,k)
dydt=-k*y+a(t);                                                         % Call ‘a’ As A Function
end