;+ ;Function: qderiv ; gets derivative of quaternion - assumes sign ambiguity has been fixed ; ;Purpose: ; ; Author: Davin Larson ; $LastChangedBy: $ ; $LastChangedDate: $ ; $LastChangedRevision: $ ; $URL: $ ;- function qderiv,t,q dq_dt = q for i=0,3 do dq_dt[*,i] = deriv(t,q[*,i]) return,dq_dt end