# How to transform between the quaternions ( or ERYs)

I know I can transform my quaternion to ERY, and it seems easier to transform between ERYs because it's more direct. For example, I have a vector X (x,y,z) and its ERY is (0,0,a), and I have another vector Y(x',y',z') and ERY is (0,0,b), if I want to get Y by doing RX+T, can I get the rotation matrix R and transformation matrix T by using TF's function? Or if its not possible, how can I compute this? Thx a lot!

@henschelx, which parameterization is ERY ? (roll,pitch,yaw) ? For roscpp, you can have a look at tf::Transform::inverseTimes to get the difference between two tf::Transform objects. For rospy, tf.transformations.py provides several utilities to get numpy matrices for transforms

Thank you so much !