my problem is it is iteration. manually it is ok. but i have any plots ánd data.

i have a figure that have many plots within.
i want
(y3-y2)/ (y2-y1)=n1

(y4-y3)/(y3-y2)=n2
(y5-y4)/(y4-y3)=n3
etc


and soon
the function of the figure is

W=8;
Wm=29
k=7;
x=2;
a=0.2
w=(0:0.3:3)
S=[1-exp(-a.*x.*k.*w)];

figure(2)
plot(w,S,'-+');

xlabel('w');
ylabel('S');

hold on