Passing a temporary parameter from time step to time step using ode113?
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Hello,
i'm using ode113 to solve some differential equations wich i stored in a function called RSDGL:
[t,F]=ode113(@RSDGL,[t0 tf],initial_conditions);
However in the function RSDGL i am using fzero to calculate zeros of functions wich appear in the differential equations as those zeros are time dependent. The problem i have is that i want to memorize those zeros temporarly to use them as starting points when i use fzero in the next time step (when ode113 calls RSDGL again). This should increase the performance as those zeros only vary little between each timestep. So i want to programm something like:
zero_new=fzero(function,zero_old);
inside my RSDGL function. I dont really have a clue how to store and overwrite those zeros and how to pass them each time ode113 calls my function RSDGL. I hope you understand my problem, as english is not my first language.
采纳的回答
This is a job for a persistent variable:
function dx = RSDGL(t, x)
persistent zero_old
if isempty(zero_old)
zero_old = 1; % Use a meaningful value!
end
zero_new = fzero(function, zero_old);
zero_old = zero_new;
...
end
It is smart to implement a method to reset this variable, e.g. for different runs of your code. Using clear RSDGL works, but I'd prefer an explicit method:
function dx = RSDGL(t, x)
persistent zero_old
if nargin == 1 % Reset!
zero_old = [];
return;
end
if isempty(zero_old)
zero_old = 1; % Use a meaningful value!
end
...
Then this resets the persistently store value:
RSDGL('reset')
This is clear and easy to understand during reading the code.
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