given an x,y,z position for the end of an robot arm(end effector), is there any way to find the roll, pitch and yaw for it...Given access to entire history of x-y-z positions. I'll be using IK then to evaluate whether these values are possible or not. All I need to find is just some 'correct' value for them....

any pointers for how to compute the roll-pitch-yaw values....