Finding q501 for Difference Equation: Solving with Matlab

[roam]

I want to find q₅₀₁ for the difference equation:

q_n=q_n-1 - 0.001 q²_n-2
n≥2,
q₀=1,
q₁=2

I thought it's easier to do this on Matlab & I tried to write a script file for this problem:

k=0.001
q(1)=1
q(2)=2
for n=1:502
    q_n=q_n-1-k*(q_n-2)^2
end

I don't know why my code isn't working/giving the right answer. Does anyone know what's the problem with this script?

 

[f95toli]

You are not indexing the array in the right way
Element n of a vector q is written q(n) in Matlab (with the first element having index 1, not zero as in some other programming languages).

Try

k=0.001
q(1)=1
q(2)=2
for n=3:502
    q(n)=q(n-1)-1-k*q(n-2)^2
end