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# how to compute derivative

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Elysi Cochin on 4 Apr 2021
Edited: darova on 5 Apr 2021 having all the values in the above equation, is the below code correct for dE(t)/d(t) computation?
dEt = beta * (1 - sigma) * St * It - (mu + alpha) * Et
what do i need to do to compute dE(t)/d(t)
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John D'Errico on 4 Apr 2021
What you have not said is explicitly WHAT you have.
What does it mean to have values?
is beta a fixed known constant? How about mu and alpha?
Is S known as a function, or do you have a list of points for S as a function of t?
Similarly for I(t). Is that known?
Is E(t) known, or are you trying to solve for E(t). That would make this a differential equation, if E is an unknown function.
Finally, do you have some sort of initial value for E(t) at some fixed value for t?

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### Accepted Answer

darova on 5 Apr 2021
Only you know initial conditions. Imagine the situation: you are throwing the ball, initial conditions are velocity and angle. Only you know how you want to throw the ball
YOu should use for loop to get solution for all your values
for i = 1:size(SIE,1) % numer of rows
S = SIE(i,1);
I = SIE(i,2);
E = SIE(i,3);
[t,E] = ode45(@(t,E) myfunc(t,S,I,E),tspan,E);
line(t,E)
end
##### 2 CommentsShowHide 1 older comment
darova on 5 Apr 2021
One curve for one set of data. You can't get one curve if you have many values and initial conditions, it's impossible
Imagine you are throwing the bal at different angles but want to get only want trajectory
One angle - one trajectory

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