Question: Is there an easy way to tell GTSAM to hold a value at the initial guess?

[Paul Furgale]

In ceres or g2o, you can easily tell the optimizer to not optimize certain parameters. is this possible in GTSAM as well?

[Jing Dong]

Put a NonlinearEquality1 factor on the variable you don't want to optimize will be a solution, but it's using penalty method will increase the nonlinearity of the object function, and sometimes cause issue..

[Frank Dellaert]

Question answered