Problem with overwriting values in vector

Hello,

my problem is with overwritting - i don't know how to overwrite vectors and save only some values. I'm solving ode ( this ode is written by me it is not ode45 or ode23 or other matlab already odefile) where i will have many values and in big netwroks i will have problem with memory - because of this i want to save only some values (for example every 4 value)

Code example of ode:

X(1) = 0.6;

Y(1)= 0.2;

licz = 1;

for tt = 1:0.05:10

l = 1;

X(l+1) = X(l) + ((X(l) *a)+(Y(l)*b));

Y(l+1) = Y(l) + (X(l)*c);

b=1;

if mod(licz,3) == 0

vector1(b) = X(l+1)

vector2(b) = Y(l+1)

end

licz=licz+1;

l=l+1

end

What i want is how to overwrite values in vector for example:

v = zeros(1,2)

step1 v = [1,0]

step2 v = [1,2]

step3 v=[2,3] (value 2 from step 2 is now on first place in vector and on second place is new value)

[madhan ravi]

What’s your desired output from the above code ? State it explicitly.

[Paulina Urban]

The desired output from the code should be vector1 and vector2 which will have values calculated by these 2 equations:

X(l+1) = X(l) + ((X(l) *a)+(Y(l)*b));

Y(l+1) = Y(l) + (X(l)*c);

Because I will work on large networks if i will write from each iteration values calculated by this two equations my memory will give an error. Because of this i need to write for example after each iteration which mod(iteration number,3) == 0 and save values solved in this iteration in a vectors.

About this equations, I'm giving first value, second value is calculated, third value is calculated (first value we can delete), fourth value is calculated (second value is calculated). I always need previous value to calcualte next value ( if I'm on iteration i then I need value from previous step i-1 ) - here i think is the problem that I can't find out how to solve it :(