Add more variables to jiminy log

[lucas-levy]

Hi,
What would be the best way to add variables to the jiminy log ?
I've tried to do something like

self.simulator.log_data["variables"]["new_column"] = np.ones_like(self.simulator.log_data["variables"]["Global.Time"])
self.simulator.write_log(path, format)

but the log generated does not contain the new_column variable.
Thank you

[duburcqa]

It is not how it works. You have to delegate this task to the controller. I don't know what you are doing. If you are doing robotics simulation without reinforcement learning, then here is the easiest way to do it:

# Keep track of the variables being manually registered.
# The user is responsible for managing their lifetime and update them.
registered_variables = []

# Define a new variable.
# It stores the "current" value that will be written in the log regularly, 
# which has to be a `np.ndarray` so that it can be updated in-place using 
# `[:] =` assignment operator (or `[()] =` for 0-d scalar arrays).
# The user is responsible for updating it manually whenever its value is 
# supposed to change, at user discretion.
registered_variables.append((["my_var_0", "my_var_1"], np.array((2,))

for fieldnames, data in registered_variables.values():
    simulator.robot.controller.register_variables(fieldnames, data)

I should add an example to document it properly.

[duburcqa]

For RL application, have a look at the documentation of BaseJiminyEnv.register_variable. It is basically the same, except that you can generate fieldnames automatically for you:

registered_variables = {}
registered_variables["my_var"] = np.array((2,))
for name, data in registered_variables.values():
    env.register_variable(name, data)