Internal function. To be applied to aes_args and identity_args,
replicates vectors of length data to length of data*frames for animation.
.lapply_rep_len(list, to_length, expected_length)A list of arguments such as those passed in aes_args and
identity_args.
Scalar number, length of the output vector; the number of rows in the data frames to replicate to.
Scalar number, the expected length of the each element
of list.
Other Internal utility:
.bind_elements2df(),
.init4proto
## This function is not meant for external use