What does this mean exactly

So me and my group have taken the divided difference method to do our project. We are using x0 as the population of Tigers and y0 as the area of the forest(s). What does it mean for our D value to come out as the same for the first group but the others are different. I will not lie this class has been confusing to me......I am needing to pretty much explain the results that we came up with. This is our code and what we got as as a result.

function D = tiger( x0, y0 )
y0=[765 850 975 1022 1100 ];
x0=[8 10 13 23 25];
D = zeros(size(x0));
    m = length(x0);
D = y0;
Do = D;
for k=2:m
    for i=k:m

        D(i)=(Do(i)-Do(i-1))/(x0(i)-x0(i-(k-1)));
      end
       Do=D;
  end
  end

Results:

tiger

ans =

    765.0000   42.5000   -0.1667   -0.1785    0.0329

Answer 1

[Bob Thompson]

D(1) does not change because you have k = 2:m, so the lowest value i can ever be is k=2.

Are you sure that x0(i-(k-1)) is correct? I admit that I have not used the divided difference method or equation before, but it seems odd to me the difference between i and k-1 should become greater with each loop.

Also, what type of class is this for? An explanation of why something is a certain way can be very different for a prob and stats class vs an economics class, even if the math appears very similar.

[Stephen23]

Amber Kollmar's "Answer" moved here:

yes x0(i-(k-1)) is correct this is the code we did in class for a class project. The class is Introduction to Numerical Analysis. We have to do a project over a real world issue so we choose tigers that are on the verge of being extinct. He told use to use the area of the forest and the population of the tigers after we told him what we choose to do. My issue is me and my partner are confused as to what do the D values actually mean?