# ode with varying constant

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prajyot gajbhiye on 21 Oct 2020
Answered: Star Strider on 21 Oct 2020
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
Ameer Hamza on 21 Oct 2020
That code will work even if you put one of the variable as scalar.

Star Strider on 21 Oct 2020
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
Use your own vector for ‘av’ and your own constant for ‘k’.

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