loop-function to count each angle and compare to the previous one

Hello!

I have got some data and calculated the regression lines at every sixth datapoint. I am able to compute the angle between the first three lines, using this script:

ax=x1(1,2)-x1(1,1); %first (a) vector
ay=y1(1,2)-y1(1,1);
bx=x1(1,3)-x1(1,2); %second (b) vector
by=y1(1,3)-y1(1,2);
cx=x1(1,1)+ax+bx; %resulting, leading to third vector
cy=y1(1,1)+ay+by;
lcx=x1(1,3)-x1(1,1); %third (c) vector 
lcy=x1(1,3)-x1(1,1);
Ba=sqrt((ax^2+ay^2)); % norm (a)
Bb=sqrt((bx^2+by^2)); % norm (b)
Bc=sqrt((lcx^2+lcy^2)); % norm (c)
alpha1=acosd(Bc^2-Bb^2-Ba^2-(2.*Ba.*Bb)); %angle in between vector a & b = a1 on the pic

Now I want to use a function that loops this, so I can calculate each angle as you can see in the picture (a1,a2,a3,....an). In a next step, I want to compare the angles with each other to find the curvature. I am not so familiar doing loops. Can you think of a loop that fits?

Thanks a lot!