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# How to put forward and backward iterations in embedded m-func block?

## How to put forward and backward iterations in embedded m-func block?

(OP)
Hello:

I'm having a m-function code, and it works perfectly when I have some workspace variables. However, it never works if i put these r,N,N1 and P as inputs to an embedded matlab function. I guess the problem is due to the clock, since m-file can have a "for x,-1,y" backward iteration loop as well as a forward loop in a same file, but Simulink clock is only forward going. So how can I actually realize the following calculation within Simulink? Please give an advice, thank you.

function [x] = abc(r,N,N1,P)

p=1;

q=1/r;

a=1;

b=0.9;

C=24.1*55*3600;
x0=C
ref=1;

for t=1:(N-mod(N,N1))/N1

S(t*N1+1)=p;
v(t*N1+1)=0.8*C*ref*p;

for k=t*N1:-1:(t-1)*N1+1

div=r+S(k+1)*b^2;
K(k)=b*S(k+1)/div;
S(k)=q+S(k+1)*r/div;
K3(k)=b*P(k)*S(k+1)/div;

v1=S(k+1)*(0.81*v(k+1)-P(k)*r)
v(k)=v(k+1)+0.6*C*q-v1/div;
Kv(k)=0.9/div;
end
x(1)=x0;
for k=(t-1)*N1+1:t*N1;
u(k)=-K(k)*x(k)+Kv(k)*v(k+1)+K3(k);
x(k+1)=x(k)+0.9*u(k)-P(k);

end

end;

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