This question is about modelling mechanical response of behavior in terms of signals My dissertation supervisor ask me to code this.

r1=.3;
r2=.5;
xh=[0.00001:.01:.21];
yh=3.2*xh-0.8;
A=2*r2*xh;
B=2*r2*yh;
R=sqrt(A.^2+B.^2);
C=xh.^2+yh.^2+r2^2-r1^2;
z=C./R;
zz=sqrt(1-z.^2);
theta2=atan2(B,A)+atan2(zz,z);
theta1=atan2((yh-r2*sin(theta2)),(xh-r2*cos(theta2)));
plot(xh,180*theta2/pi)
hold on
plot(xh,180*theta1/pi,'r')
axis([0 .2 -170 0])
xlabel('xh [m]')
ylabel('\theta [degree]')
legend('\theta_2','\theta_1')
title 'The change in angles between the elbow and shoulder while lifting a heavy Load' grid


I understand it but now he has ask me to..

" Please do the links velocities and send me the results, please plot velocity of the links against yh, limit the axis of yh to be  ‘axis([-.76 -.16  -15 5])’"

I know that length of r1 or r2 multiplied by theta1 or theta2 should give arc length. Then arc length divided by a time interval will give rad/sec
which i can plot against yh...........I dont know what this axis([-.76 -.16  -15 5])’ means...... BUT I AM VERY NEW TO MATLAB HELP PLEASE.
I dont know what this axis([-.76 -.16 -15 5])’ means


As far as I am concerned axis([-.76 -.16 -15 5]) set minimal and maximum values for x axis (first and second values) and y axis (third and forth values) in plot.

For example:

x = linspace (-10, 10, 100);
y = x .^ 2;
plot (x, y, 'r', "linewidth", 2);
title ("S");
xlabel ("x");
ylabel ("y");




x = linspace (-10, 10, 100);
y = x .^ 2;
plot (x, y, 'r', "linewidth", 2);
title ("S");
xlabel ("x");
ylabel ("y");
axis ([-5, 5, -5, 20]);