fwd_kin(q,x)

function X = fwd_kin(q,x)
% given a position in the configuration space, calculate the position of
% the end effector in the workspace for a two-link manipulator.

% q: vector of joint positions
% x: design vector (link lengths)
% X: end effector position in cartesian coordinates

% configuration space coordinates:
q1 = q(1);              % theta 1
q2 = q(2);              % theta 2

% manipulator parameters:
l1 = x(1);              % link 1 length
l2 = x(2);              % link 2 length

% calculate end effector position:
X = [l1*cos(q1) + l2*cos(q1+q2)
    l1*sin(q1) + l2*sin(q1+q2)];