Calling a function in function considering a loop

Hi

I have a function like c=F(i,j)

I want to create a loop in my function as below

for p=1:4
    c=c+x*F(i-p,j)
end 

I want to have this

c=F(3,1) + F(2,1) +F(1,1)

By doing that, unfortunetaly, the MATLAB does not condider all the loops and when i=i-p, it immidiately goes out from the function and just consider F(3,1)

I appreciate that if u tell me how i can do sth like this.

[KSSV]

Show us your full code along with the function F. Are you running a loop for i,j ??

[Mohsen]

function CB=F(i,j)
global Z
N=3;
CB=0;
TC=[7,4,5,6,5,8];
LL=[2,3,1,1,1,1];
persistent G
if isempty(G)
    G=ones(N,1);
end 
if i==1 
    for p=1:(N-1)
        G(i,1)=0;
        if G(p+i,1)==0
            CB=CB+TC(1)/(N-1);
        else
            CB=LL(p)*G(1+p,1)*A(1+p,j)+TC(1)/(N-1);
        end
    end
elseif i==N
    for p=1:(N-1)
        G(i,1)=0;
        CB=CB+LL(p)*G(i-p,1)*B(i-p,j)+TC(i)/(N-1);
    end
else
    for p=1:(i-1)
        G(i,1)=0;
        if (G(i-p,1)==0)
            continue;
        else 
            CB=CB+LL(p)*G(i-p,1)*B(i-p,j)+TC(i)/(i-1);
        end 
    end 
    for p=1:(N-i)
        if (G(i+p,1)==0)
            continue;
        else 
            CB=LL(p)*G(i+p,1)*A(i+p,j);
        end 
    end 
end 
end 
function a=A(i,j)
global Z
global G
Z=i;
G(i,1)=0;

a=F(i,j);
end 

Answer 1

[Mathieu NOE]

hello

here you are.

NB I prefered not to use the same "c" variable name both in the function and in the main loop - not that it's forbidden or a coding mistake, simply this is prone to errors and does not ease the code reading / debugging.

% init 
c = 0; % init c = zero

i = 4;
j = 1; 
x = 1;

% main code

for p = 1:3
    c = c+x*F(i-p,j);
end


% function 
function out = F(i,j)

    out = 5*i + 10*j;

end

[Mohsen]

Thanks for your quick reply.

In my case, N=i=4, the problem is that F(1,1)= constant value and the first loop is

for p=1:i
    F(4,1)= x*F(3,1) + y*F(2,1) + z*F(1,1)
end 

Then I sould have

for 1:i
    F(3,1) =y*F(2,1) + z*F(1,1)
end 

and so on, till i==1

I think I cannot write the loop outside the function like you did.

Apart from that, N has a high value not just 4.

best regards

Mohsen

[Rik]

It sounds like you need recursion. But more importantly: you need to thouroughly describe what you actually need. Where are y and z suddenly coming from?

The only viable path to a good solution is a good description of the problem.

[Mohsen]

Well z and y are 2 constants.

As you mentioned, I surely need recursion.

The F(i,j) is a function of F(i-p,j) where p=1:i.

So

F(i,j)=constant*F(i-1,j) + constant*F(i-2,j)+ ... + constnat*F(1,j) eq(1)

And again

F(i-1,j)= onstant*F(i-2,j) + constant*F(i-3,j)+ ... + constnat*F(1,j).

Until

F(2,j)= constant*F(1,j)

The problem is that in the eq(1) the for loop does not run completely and when the compiler reachs F(i-1,J). It goes out from the loop.

At the first step, I want the loop runs completely and then all functions (F(i-1,j) ...) recall.