Mark Miller

In short, it adds a -r / --start flag to start looking at particular results, i.e, the 100th result.

v3

summarize motion pairs and summarize motion returns different values - one needs to be unnested, the other doesn't. is there a preference of what to return?

- it says it is pairs (rather than sessions) - head_n or n or head?

``` Error in `cross()`: ! `cross` expects both arguments to inherit from `dddr_vector3`. Instead, the arguments were `NULL` and `NULL`. Backtrace: 1. dddr::rotate(...) 2. dddr:::rotate.dddr_quat(...) 3. dddr:::make_rotator(axis, angle, from, to)...

add `bundle_vector`

2

usually I do something like ``` df %>% mutate(Pos = vector3(Posx, Posy, Posz), .keep="unused") ``` what if I could do something like ``` df %>% bundle_vector(Pos) # or bundle_vector(Pos="Pos{d}") ```...

https://github.com/krlmlr/awesome-vctrs

It'd be nice to compute the scalar angle between two rotations According to a researchgate.com forum post, that is: theta = 2*asin(norm of the vector part of the quaternion product...