Idea: identity method for Lie groups

[spencer kraisler]

Hello,

I am working on a script right now that involves dealing with the state space of a robot arm. The state space is simply SO(2)^k, where k is the number of joints. There are a few instances where I'd like to have the identity element readily available. Ofc this is just (I2, I2, ..., I2). However it would be nice if Lie group manifolds had a .identity() method that would just give you it. This library has nice and clean syntax, so I felt such a method would fit nicely. I'd be happy to help write this too. 

Best,

Spencer 

[Nicolas Boumal]

Hello Spencer,

That makes sense, and it would be fine to add it to the code base: various manifolds already have their own idiosyncratic functions provided by the factory.

Feel free to issue a pull request where you add the M.lie_identity() function. It would make sense to add it to complexcirclefactory as well. In fact, even the Euclidean spaces would make sense (lie_identity of R^n is just the zero vector, seeing it as a translation group). Notice that I just pushed the other changes to rotationsfactory, so you may want to pull before pull-requesting edits.

Thanks!

Nicolas

[spencer kraisler]

Awesome, I sent a pull request! Let me know if there are any issues.

Best,

Spencer

[spencer kraisler]

Hi Nicolas,

I pushed your suggestions to my fork. I was wondering if you could tell me if this is on the right track. 

Best,

Spencer

[Nicolas Boumal]

Done: I replied to you on github. Thanks!