Default behaviour is to print by rows.  To print by columns, set
  option show_onions_horizontally to TRUE:
options("show_onions_horizontally" = TRUE)
Any non-TRUE value (including NULL and its being unset)
  will restore the default.
Similarly, to show onions compactly,  set option
  show_onions_compactly to TRUE:
  
options("show_onions_compactly" = TRUE)
This option works best for simple onions with integer entries (or at
  least values with few decimal places), and especially if there are
  many zero entries.
Function onion_show() is a helper function, not really intended
  for the end-user.
The “names” of the components of an onion (viz Re,
  i, j, k for quaternions and Re, i,
  j, k, l,il,jl,kl for
  octonions) are given by function comp_names() which takes
  either a character string or an onion.