access a page in 3d matrix at time t in ode45

i am solving for the g matrix in LQT control- before that i solved p for t[0:20] and i got a 3d matrix. to solve g i need a certain page in P matrix at every t sample in the ode45 solver. how can i achieve that

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this is the piece of code in the main code

[tp,p]=ode45(@(t,p)mRiccati2(tp, p, A, B,C, Q , R), tspan,pf);

P=reshape(P',size(A,1),size(A,2),size(T,1));

[tg,g]=ode45(@(tg,g)Gfunc2(tg, g, A, B, C, Q , R , Z),tp, gf);

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this is mReccati2:

function dXdt = mRiccati2(t, X, A, B ,C, Q, R)

X = reshape(X, size(A));

E= B*inv®*B.';

dXdt = -A.'*X - X*A + X*E*X - C.'.*Q.*C ;

dXdt = dXdt(:);

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this is function g "where the problem present":

function dXdt = Gfunc(t, X, A, B, C, Q, R , Z)

global p tp P

E= B*inv®*B.';

W=C.'.*Q;

dXdt= (interp1(tp,P(:,:,????),t).*E - A.')*X -C.'.*Q.*Z;

 "i need to access certain page every time sample."

[Jan]

How could we know, what you need instead the "????"? The explanation "access certain page every time sample" does not define clearly, what you need here. But there is a general problem:

Using interp1 in a function to be integrated is a bad idea, because the result is not smooth. See http://www.mathworks.com/matlabcentral/answers/59582#answer_72047. Matlab's integrators cannot handle non-smooth functions correctly. If you are lucky, you get an error message, but without luck you get a final value, which is dominated by rounding errors.

The explicit calculation of the inverse of a matrix is deprecated. See:

doc inv

[mohamed elkattan]

well,i got your point here but i can't come with a better idea the problem here is that

for every output g in a time sample in t i need a page in P

that is: at page(i) in p i get a g(i) every t sample