I have a script but i didn't understand the flow of the program could anybody please give me an explanation for this script?

%%Plotting the terrain profile
x1 = -35:0.001:3;
x2 = 3.001:0.001:25;
x3 = 25.001:0.001:100;
x4 = 100.001:0.001:160;
% Values of slope for all the slope equations
m1 = 0;
m2 = 0;
m3 = 0.133333;
m4 = -0.02;
% Values of constant for all the slope equations
c1 =15; 
c2 =0;  
c3 =0; 
c4 =10; 
% Slope equations
y1 = m1.*(x1)+c1;
y2 = m2.*(x2-10)+c2; 
y3 = m3.*(x3-25)+c3;
y4 = m4.*(x4-100)+c4;
% Plotting the terrain profile
x=[x1 x2 x3 x4]';
y=[y1 y2 y3 y4]';
figure(1)
plot(x,y); % Plotting the Ground elevation vs distance
ylim([0 25]);
xlabel('Distance [m]');
ylabel('Ground Elevation');
title('Ground Elevation vs distance (m)');

[Parth Panchal]

Thanks Matt ! Can you please explain me about the slope calculation?

Answer 1

[Walter Roberson]

For the code

y1 = m1.*(x1)+c1;
y2 = m2.*(x2-10)+c2; 
y3 = m3.*(x3-25)+c3;
y4 = m4.*(x4-100)+c4;

the lines after the first are "translating" the standard y = m*x+b to start at x=10, x=25, and x=100 respectively.

Mathematically these adjustments to x could also be folded into the c constants by increasing the c constants by -m2*10, -m3*25, and -m4*100 respectively, like

y2 = m2 .* x2 + (c2-m2*10)

It is just changing the intercept of the line in a way that is easier to think about in this case.